Patent Publication Number: US-2010121216-A1

Title: Bioelectrical impedance measurement body attachment unit and body fat measurement device

Description:
TECHNICAL FIELD 
     The present invention relates to a bioelectrical impedance measurement body attachment unit attached by being wrapped around a body of a subject to measure a bioelectrical impedance, and a body fat measurement device for calculating a body fat mass of the subject by measuring the bioelectrical impedance using the bioelectrical impedance measurement body attachment unit. 
     BACKGROUND ART 
     A body fat mass is recently being given attention as one index for knowing a health condition of a subject. In particular, a visceral fat mass is given attention as an index for making determination on whether or not a visceral obesity is present. The visceral obesity is said to induce lifestyle-related diseases that easily causes arterial sclerosis such as diabetes, a high blood pressure and hyperlipemia, and the use of the above index is expected from a standpoint of preventing such diseases. In this case, the visceral fat is a fat that accumulates around internal organs on an inner side of an abdominal muscle, and is distinguished from a subcutaneous fat that accumulates on a surface layer of the abdomen. An area (hereinafter referred to as visceral fat area) occupied by the visceral fat at a cross section of the abdomen of a portion corresponding to an umbilicus position is generally adopted for the index indicating the visceral fat mass. 
     Normally, an image analyzing method using a tomographic image of the abdomen photographed using an X-ray CT (Computer Tomography) or an MRI (Magnetic Resonance Imaging) is used to measure the visceral fat mass. In such an image analyzing method, the visceral fat area is calculated from the acquired tomographic image of the abdomen. However, in order to use such a method, a large facility that may be installed in medical institutions such as the X-ray CT and the MRI is required, and thus the visceral fat mass is very difficult to measure on a daily basis. A problem of exposure also arises when the X-ray CT is used, and thus such a method may not necessarily be a preferable measurement method. 
     As a measurement method taking the place thereof, application of a bioelectrical impedance method is being reviewed. The bioelectrical impedance method is a method of measuring the body fat mass widely used in a body fat measurement device for domestic use, where electrodes are brought into contact with four limbs, and the bioelectrical impedance is measured using such electrodes to calculate the body fat mass from the measured bioelectrical impedance. The above-described body fat measurement device accurately measures a degree of accumulation of the body fat by sites of the body such as the entire body or four limbs, or the body (trunk of the body), and is widely used in households and the like. 
     However, the conventional body fat measurement device measures the degree of accumulation of the body fat by sites of the body such as the entire body or four limbs, or the body (trunk of the body) as described above, and does not individually extract and accurately measure the degree of accumulation of the visceral fat or the degree of accumulation and the subcutaneous fat. This is because the body includes not only the visceral fat but also the subcutaneous fat, as described above, and thus accurately measuring the visceral fat mass and the subcutaneous fat mass individually is difficult in the body fat measurement device described above. 
     In order to solve such problems, consideration is being made of bringing an electrode directly in contact with the body, measuring the bioelectrical impedance using the electrode, and accurately measuring the visceral fat mass and the subcutaneous fat mass individually based thereon. For instance, Japanese Unexamined Patent Publication No. 2002-369806 (Patent Document 1) discloses a body fat measurement device configured such that the electrode is arranged in contact with the body by arranging an electrode on an inner peripheral surface of a belt member and wrapping and fixing the belt member to the body. The body fat measurement device disclosed in Japanese Unexamined Patent Publication No. 2002-369806 enables highly accurate measurement of the visceral fat mass and the subcutaneous fat mass, which has been difficult in the related art, by measuring the bioelectrical impedance using the electrode arranged in contact with the body of the subject using the belt member. 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2002-369806 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     When measuring a bioelectrical impedance using the above-described bioelectrical impedance method, measurement is carried out by bringing an electrode directly in contact with a part of a body of a subject, and thus it is important to stably maintain a pressing strength of the electrode with respect to the body surface constant for every measurement. However, this is not easy to achieve as a shape and a size of the body of the subject differ among individuals. In particular, a difference among individuals is large in the shape and the size of the body, where stably ensuring the pressing strength of the electrode with respect to the body is very difficult when arranging the electrode so as to be in contact with the body of the subject using the bioelectrical impedance measurement body attachment unit including a belt member. 
     For instance, in the bioelectrical impedance measurement body attachment unit of the body fat measurement device disclosed in Japanese Unexamined Patent Publication No. 2002-369806, a wrapping strength of the belt member differs for every attachment as a attachment task of the belt member to the body is carried out manually, and thus the pressing strength of the electrode with respect to the body also differs for every attachment as a result. 
     In the case where the pressing strength of the electrode with respect to the body surface varies, such a variation appears as a variation of a contact resistance between the electrode and a body surface, which may lower the measurement accuracy. Therefore, it is very important that the bioelectrical impedance measurement body attachment unit is configured such that the electrode is always stably pressed against the body of the subject with a constant load regardless of the subject for every measurement. 
     On the other hand, in the case where the belt member is strongly wrapped around the body of the subject to ensure the pressing strength of the electrode with respect to the body, the body of the subject is tightened by the belt member, which may be painful to the subject. In particular, as the shape of the body (in particular, abdomen of the body) fluctuates with breathing motion (normally, a body peripheral length increases in inhaling motion and the body peripheral length reduces in exhaling motion), the user may feel a strong oppressing feeling in the inhaling motion, which may force great pain on the subject. 
     In the case where the bioelectrical impedance is measured with the electrode in contact with the body of the subject, a value of the measured bioelectrical impedance is known to fluctuate with the breathing motion of the subject. Major factors thereof being that the shape of the body changes with the breathing motion and a body composition between the electrodes arranged in contact with the body fluctuates, that the distance between the electrodes fluctuates with change in the shape of the body, that the contacting state of the electrode and the body surface fluctuates and the contact resistance changes, or the like. The fluctuation in the value of the bioelectrical impedance involved in such breathing motion inhibits the high accuracy measurement of a visceral fat mass and a subcutaneous fat mass, whereby some kind of measures needs to be taken. 
     In view of solving the above problems, it is an object of the present invention to provide a bioelectrical impedance measurement attachment unit that enables the electrodes to be pressed against the body of the subject at satisfactory reproducibility with a constant load in the attachment state and that does not give pain to the subject, and a body fat measurement device equipped with the same, and also to provide a body fat measurement device capable of detecting the breathing state of the subject at high accuracy and measuring the body fat mass, in particular, the visceral fat mass and the subcutaneous fat mass at high accuracy. 
     Means for Solving the Problems 
     In accordance with one aspect of the present invention, a bioelectrical impedance measurement body attachment unit according to the present invention is attached to a body of a subject to measure a bioelectrical impedance, the bioelectrical impedance measurement body attachment unit including: a plurality of electrodes arranged in contact with a surface of the body of the subject; an electrode support for supporting the plurality of electrodes; and a long belt to be wrapped around the body of the subject in an attached state to attach the electrode support to the body of the subject. The electrode support includes a fixing portion fixed with one end of the belt in a relatively immovable manner with respect to the electrode support, and a holder for holding a portion closer to another end of the belt in a relatively movable manner with respect to the electrode support in the attached state. The holder includes an attachment portion removably attachable to an arbitrary position of the portion closer to the other end of the belt, and a biasing portion for coupling the attachment portion and the electrode support in the attached state, and biasing the attachment portion and the electrode support in an approaching direction. 
     According to such a configuration, since the attachment portion and the electrode support attached to an arbitrary position of the portion closer to the other end of the belt are coupled by the biasing portion in the attached state, the portion closer to the other end of the belt is constantly pulled towards the electrode support side based on the biasing force of the biasing portion. Thus, the body of the subject is tightened with substantially a constant tightening strength by the bioelectrical impedance measurement body attachment unit based on the biasing force of the biasing portion, and the electrodes can be pressed against the body of the subject with a substantially constant load. With the above-described configuration, the attachment portion can be attached to an arbitrary position of the portion closer to the other end of the belt, and thus the bioelectrical impedance measurement body attachment unit can be closely attached to the body of the subject with satisfactory reproducibility regardless of a body peripheral length of the subject by attaching the attachment portion to an appropriate position of the belt. Furthermore, with the above-described configuration, a wrapping length of the bioelectrical impedance measurement body attachment unit changes following the breathing motion of the subject by appropriately adjusting the biasing force of the biasing portion, and thus the subject does not feel an excessive oppressing feeling, and a bioelectrical impedance measurement body attachment unit that is not painful to the subject can be obtained. 
     In the bioelectrical impedance measurement body attachment unit according to the present invention, the biasing portion is preferably arranged on either the attachment portion or the electrode support, and in this case, preferably, the biasing portion is removably attached to the other one of the attachment portion or the electrode support. 
     According to such a configuration, the attachment portion and the electrode support can be coupled by the biasing portion after attaching the attachment portion to an appropriate position of the belt when attaching the bioelectrical impedance measurement body attachment unit, and thus an attachment task is greatly facilitated, and a bioelectrical impedance measurement body attachment unit excelling in handability can be obtained. 
     In the bioelectrical impedance measurement body attachment unit according to the present invention, the biasing portion preferably includes a spring member or a rubber member serving as a biasing force expressing member. 
     Therefore, the tightening strength with respect to the body of the subject in the attached state can be appropriately set with a very simple configuration by using a spring member or a rubber member for the biasing portion. 
     In the bioelectrical impedance measurement body attachment unit according to the present invention, the biasing portion preferably has a mechanism of maintaining constant a tensile force of the belt wrapped around the body of the subject in the attached state. 
     According to such a configuration, the body of the subject is always tightened with a constant tightening strength by the bioelectrical impedance measurement body attachment unit, and thus the electrodes can always be pressed against the body of the subject with a constant load. 
     In the bioelectrical impedance measurement body attachment unit according to the present invention, the biasing portion preferably includes a constant load spring serving as a biasing force expressing member. 
     By using a constant load spring for the biasing portion in this manner, the tightening strength with respect to the body of the subject in the attached state can be easily set constant. 
     According to another aspect of the present invention, a body fat measurement device according to the present invention includes: a bioelectrical impedance measurement body attachment unit according to the present invention; an impedance measuring portion for measuring a bioelectrical impedance of a subject using the plurality of electrodes; and a body fat mass calculating portion for calculating a body fat mass of the subject based on the bioelectrical impedance measured by the impedance measuring portion. 
     According to such a configuration, there is obtained a body fat measurement device including a bioelectrical impedance measurement body attachment unit which enables the electrodes to be pressed against the body of the subject with a substantially constant load with satisfactory reproducibility in the attached state and which is not painful to the subject. Therefore, a body fat measurement device capable of calculating the body fat mass at high accuracy can be obtained. 
     Preferably, the body fat measurement device according to the present invention further includes: a body peripheral length measurement unit for measuring a body peripheral length of the subject by detecting a wrapping length of the belt wrapped around the body of the subject with the bioelectrical impedance measurement body attachment unit attached to the body of the subject, and in this case, the body fat mass calculating portion preferably calculates the body fat mass of the subject based on the bioelectrical impedance measured by the impedance measuring portion and the body peripheral length of the subject measured by the body peripheral length measurement unit. 
     According to such a configuration, the body peripheral length of the subject can be easily and automatically measured by attaching the bioelectrical impedance measurement body attachment unit, and the body fat can be measured at high accuracy by calculating the body fat mass using the obtained body peripheral length. 
     Preferably, the body fat measurement device according to the present invention further includes: a body peripheral length fluctuation amount measurement unit for detecting fluctuation of a body peripheral length of the subject by detecting fluctuation of the wrapping length of the belt wrapped around the body of the subject with the bioelectrical impedance measurement body attachment unit attached to the body of the subject; and a breathing state detecting portion for detecting a breathing state of the subject based on the fluctuation of the body peripheral length of the subject measured by the body peripheral length fluctuation amount measurement unit; and in this case, the body fat mass calculating portion preferably calculates the body fat mass of the subject based on the bioelectrical impedance measured by the impedance measuring portion and information on the breathing state detected by the breathing state detecting portion. 
     According to such a configuration, the breathing state of the subject can be detected at high accuracy with a simple configuration of detecting the fluctuation of the wrapping length of the belt of the bioelectrical impedance measurement body attachment unit during the measurement. Through the use of such a detection method, the change in the body peripheral length of the subject involved in the breathing motion can be captured at high accuracy, and thus a body fat measurement device capable of calculating the body fat mass at high accuracy can be obtained. 
     In the body fat measurement device according to the present invention, the body fat calculating portion preferably extracts the bioelectrical impedance measured at a timing of transitioning from an exhaling motion to an inhaling motion detected by the breathing state detecting portion from time-series data of the bioelectrical impedance measured by the impedance measuring portion, and calculates the body fat mass of the subject from the extracted bioelectrical impedance. 
     According to such a configuration, the bioelectrical impedance can be measured excluding an influence of the fluctuation of the bioelectrical impedance that occurs with the breathing motion, and thus the body fat mass can be calculated at high accuracy. 
     In the body fat measurement device according to the present invention, the body fat mass calculating portion preferably includes a visceral fat mass calculating part for calculating a visceral fat mass of the subject. 
     The bioelectrical impedance needs to be measured with the electrodes arranged in contact with the body of the subject in order to measure the visceral fat mass at high accuracy, and thus the visceral fat mass can be particularly calculated at high accuracy with the body fat measurement device of the above configuration. 
     In the body fat measurement device according to the present invention, the body fat mass calculating portion preferably includes a subcutaneous fat mass calculating part for calculating a subcutaneous fat mass at an abdomen of the subject. 
     The bioelectrical impedance needs to be measured with the electrodes arranged in contact with the body of the subject in order to measure the subcutaneous fat mass at the abdomen at high accuracy, and thus the subcutaneous fat mass at the abdomen can be particularly calculated at high accuracy with the body fat measurement device of the above configuration. 
     Effects of the Invention 
     According to the present invention, a bioelectrical impedance measurement body attachment unit which enables electrodes to be pressed against a body of a subject with a constant load in an attached state with satisfactory reproducibility and which is not painful to the subject, and a body fat measurement device equipped with the same are provided, and furthermore, a body fat measurement device capable of detecting a breathing state of the subject at high accuracy and capable of measuring a body fat mass, particularly, a visceral fat mass and a subcutaneous fat mass at high accuracy is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing function blocks of a body fat measurement device according to a first embodiment of the present invention. 
         FIG. 2  is a flowchart showing operation procedures of the body fat measurement device in measuring a visceral fat area, a subcutaneous fat area, and a body fat percentage using the body fat measurement device according to the first embodiment of the present invention. 
         FIG. 3  is a view showing an outer appearance structure of the body fat measurement device according to the first embodiment of the present invention, and is a perspective view showing a state where various types of attachment units arranged in the body fat measurement device are attached to the subject. 
         FIG. 4  is a perspective view showing an outer appearance structure of a bioelectrical impedance measurement abdomen attachment unit according to the first embodiment of the present invention. 
         FIG. 5  is a bottom view showing an outer appearance structure of the bioelectrical impedance measurement abdomen attachment unit according to the first embodiment of the present invention. 
         FIG. 6  is a cross-sectional view taken along line VI-VI shown in  FIGS. 4 and 5  of the bioelectrical impedance measurement abdomen attachment unit according to the first embodiment of the present invention. 
         FIG. 7  is a schematic cross-sectional view showing a state where the bioelectrical impedance measurement abdomen attachment unit according to the first embodiment of the present invention is attached to the abdomen of the subject. 
         FIG. 8A  is a perspective view describing a detailed structure of a holder of the bioelectrical impedance measurement abdomen attachment unit according to the first embodiment of the present invention. 
         FIG. 8B  is a perspective view describing a detailed structure of the holder of the bioelectrical impedance measurement abdomen attachment unit according to the first embodiment of the present invention. 
         FIG. 9  is a schematic view showing an internal structure of an attachment portion of the holder of the bioelectrical impedance measurement abdomen attachment unit according to the first embodiment of the present invention. 
         FIG. 10  is a view showing function blocks of a body fat measurement device according to a second embodiment of the present invention. 
         FIG. 11  is a function block diagram showing a specific configuration of a waist length measurement unit of the body fat measurement device according to the second embodiment of the present invention. 
         FIG. 12  is a bottom view of a belt of a bioelectrical impedance measurement abdomen attachment unit according to the second embodiment of the present invention. 
         FIG. 13  is a perspective view showing a structure of a holder of the bioelectrical impedance measurement abdomen attachment unit according to the second embodiment of the present invention. 
         FIG. 14  is a schematic cross-sectional view of a belt feeding portion of the holder of the bioelectrical impedance measurement abdomen attachment unit according to the second embodiment of the present invention. 
         FIG. 15  is a graph showing a relationship of a fluctuation of the waist length of the subject and the bioelectrical impedance that varies from hour to hour. 
         FIG. 16  is a flowchart showing the operation procedures of the body fat measurement device in measuring the visceral fat area, the subcutaneous fat area, and the body fat percentage using the body fat measurement device according to the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
           1 A, 1 B body fat measurement device 
           10  control unit 
           11  calculation processing section 
           12  impedance measuring portion 
           13  body fat mass calculating portion 
           14  total fat mass calculating part 
           15  site type fat mass calculating part 
           16  visceral fat mass calculating part 
           17  subcutaneous fat mass calculating part 
           18  breathing state detecting portion 
           21  constant current generation unit 
           22  terminal switching unit 
           23  potential difference detection unit 
           24  physical information measurement unit 
           25  subject information input unit 
           26  display unit 
           27  operation unit 
           28  power supply unit 
           29  memory 
           30  waist length measurement unit 
           100 A,  100 B bioelectrical impedance measurement abdomen attachment unit 
           110  electrode support 
           111  sheet-like portion 
           112  electrode support mechanism accommodating portion 
           113  electrode 
           113   a  rod portion 
           113   a   1  collar portion 
           113   b  plate-shaped portion 
           114  fixing portion 
           115  holder 
           116  guide frame 
           116   a  base body 
           116   b  lid body 
           117  coil spring 
           118  connector 
           119  positioning through-hole 
           120  belt feeding portion 
           121  pulley with teeth 
           122  hook 
           124  photoelectronic sensor 
           125  rotary encoder 
           126  detection shaft 
           130  attachment portion 
           131  band winding mechanism 
           132  reel body 
           133  band 
           134  spring accommodating portion 
           134   a  protrusion spring 
           135  buckle 
           136  fixing mechanism 
           137  push button 
           138  relay member 
           138   a  spring 
           139  turning lock member 
           139   a  locking nail 
           140  belt 
           141  one end 
           142  other end 
           144  encoder strip 
           145   a,    145   b  barcode element 
           151  waist length measurement circuit 
           165  device main body 
           172 A,  172 B bioelectrical impedance measurement upper limb attachment unit 
           173 A,  173 B bioelectrical impedance measurement lower limb attachment unit 
           180  connection cable 
           300  subject 
           301  abdomen 
           302 A,  302 B wrist 
           303 A,  303 B ankle 
           400  bed surface 
         A 11 , A 12 , A 21 , A 22  abdominal electrode 
         F 11 , F 12 , F 21 , F 22  lower limb electrode 
         H 11 , H 12 , H 21 , H 22  upper limb electrode 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention will be described in detail below with reference to the drawings. In each embodiment shown below, a bioelectrical impedance measurement body attachment unit applied with the present invention aimed to be attached to an abdomen of a subject will be described by way of example. Thus, in each embodiment shown below, the bioelectrical impedance measurement body attachment unit applied with the present invention is particularly referred to as “bioelectrical impedance measurement abdomen attachment unit”. The body fat measurement device in each embodiment below is configured to include the bioelectrical impedance measurement abdomen attachment unit serving as the bioelectrical impedance measurement body attachment unit described above. Note that the body fat measurement device in each embodiment described below is configured to be able to individually measure a visceral fat mass and a subcutaneous fat mass, but is a body fat measurement device configured to be able to measure not only the visceral fat mass and the subcutaneous fat mass, but also to measure the fat mass (total fat mass) of the entire body or the fat mass (fat mass of upper limb and lower limb, fat mass of the body, etc.) by a specific site of the body. 
     First, prior to describing the bioelectrical impedance measurement abdomen attachment unit and the body fat measurement device quipped with the same in each embodiment of the present invention, various terms representing a site of the body will be defined. “Body” refers to a portion excluding a head, a neck, and four limbs of the body, and a portion corresponding to a so-called trunk of the body including a chest and the abdomen. “Abdomen” refers to a portion positioned on the lower limb side when the body is divided to the portion positioned on the neck side (i.e., chest), and a portion positioned on the lower limb side, and includes an abdomen front surface and an abdomen rear surface. The “abdomen front surface” refers to a body surface of a portion visible when the subject is observed from the front surface side of the surface of the abdomen of the subject. The “abdomen rear surface” refers to a body surface of a portion visible when the subject is observed from the rear surface side of the surface of the abdomen of the subject. The “site distant from the abdomen” includes the upper limb including an upper arm, a forearm, a wrist, and fingers, the chest distant by greater than or equal to a predetermined distance (e.g., about 10 cm) from a portion where a diaphragm is positioned, the neck and the head, and the lower limb including a thigh, a lower thigh, an ankle, and toes. “Body axis” refers to an axis extending in a direction substantially perpendicular to a transverse section of the abdomen of the subject. 
     First Embodiment 
       FIG. 1  is a view showing function blocks of a body fat measurement device according to a first embodiment of the present invention. First, a configuration of the function blocks of a body fat measurement device  1 A according to the present embodiment will be described with reference to  FIG. 1 . 
     As shown in  FIG. 1 , a body fat measurement device  1 A according to the present embodiment mainly includes a control unit  10 , a constant current generation unit  21 , a terminal switching unit  22 , a potential difference detection unit  23 , a physical information measurement unit  24 , a subject information input unit  25 , a display unit  26 , an operation unit  27 , a power supply unit  28 , a memory  29 , and a plurality of electrodes A 11 , A 12 , A 21 , A 22 , H 11 , H 12 , H 21 , H 22 , F 11 , F 12 , F 21 , and F 22  attached to the body. The control unit  10  includes a calculation processing section  11 . The calculation processing section  11  includes an impedance measuring portion  12 , and a body fat mass calculating portion  13 . 
     The control unit  10  is configured by a CPU (Central Processor Unit) and the like, and controls the overall body fat measurement device  1 A. Specifically, the control unit  10  sends a command to the various types of function blocks described above or performs various types of calculation processes based on the obtained information. The various types of calculation processes are performed by the calculation processing section  11  arranged in the control unit  10 . 
     The plurality of electrodes includes abdominal electrodes A 11 , A 12 , A 21 , A 22  to be attached to the abdomen of the subject, upper limb electrodes H 11 , H 12 , H 21 , H 22  to be attached to the upper limb of the subject, and lower limb electrodes F 11 , F 12 , F 21 , F 22  to be attached to the lower limb of the subject. 
     The abdominal electrodes A 11 , A 12 , A 21 , A 22  are arranged in the bioelectrical impedance measurement abdomen attachment unit (bioelectrical impedance abdomen attachment unit according to the present embodiment)  100 A including a band-shaped member to be wrapped around the body of the part including the abdomen of the subject, and are attached to the surface of the abdomen of the subject with each electrode aligned along a body axis direction by attaching the bioelectrical impedance measurement abdomen attachment unit  100 A to the abdomen of the subject. In this case, the abdominal electrodes A 11 , A 12 , A 21 , A 22  may be attached to the abdomen front surface of the subject, or may be attached to the abdomen rear surface of the subject. An abdominal electrode group, where four abdominal electrodes A 11 , A 12 , A 21 , A 22  form one set, may be attached to the abdomen in plural sets parallel to each other. In such a case, the abdominal electrode group of all of the sets may be attached to only one of either the abdomen front surface or the abdomen rear surface, or the abdominal electrode group of some sets may be attached to the abdomen front surface and the abdominal electrode group of the remaining sets may be attached to the abdomen rear surface. 
     The upper limb electrodes H 11 , H 12 , H 21 , H 22  are attached to one of the sites of the upper limb corresponding to the site distant from the abdomen of the subject, and one pair thereof is suitably attached to the surface of the wrist of the right hand and the surface of the wrist of the left hand, respectively. The lower limb electrodes F 11 , F 12 , F 21 , F 22  are attached to one of the sites of the lower limb corresponding to the site distant from the abdomen of the subject, and one pair thereof is suitably attached to the surface of the ankle of the right foot and the surface of the ankle of the left foot, respectively. The abdominal electrodes A 11 , A 12 , A 21 , A 22 , the upper limb electrodes H 11 , H 12 , H 21 , H 22 , and the lower limb electrodes F 11 , F 12 , F 21 , F 22  are respectively electrically connected to the terminal switching unit  22 . 
     The terminal switching unit  22  is configured by a relay circuit, and the like, and electrically connects a specific electrode selected from the plurality of electrodes and the constant current generation unit  21  and electrically connects a specific electrode selected from the plurality of electrodes and the potential difference detection unit  23  based on a command inputted from the control unit  10 . Thus, the electrode electrically connected to the constant current generation unit by the terminal switching unit  22  functions as a constant current application electrode, and the electrode electrically connected to the potential difference detection unit  23  by the terminal switching unit  22  functions as a potential difference detection electrode. The electrical connection by the terminal switching unit  22  is switched in various manners during the measurement operation. Normally, the constant current application electrode and the potential difference detection electrode are respectively configured by a pair of electrodes, where each of the pair of electrodes as referred to herein includes both single electrode or a plurality of electrodes. In other words, each of the pair of electrodes can be configured by handling even the separately and independently arranged electrode in an electrically equivalent manner. 
     The constant current generation unit  21  generates a constant current based on a command inputted from the control unit  10 , and supplies the generated constant current to the constant current application electrode through the terminal switching unit  22 . A high frequency current (e.g., 50 kHz, 500 μA) suitably used to measure the body composition information is selected for the constant current generated in the constant current generation unit  21 . Thus, the constant current is applied to the subject through the constant current application electrode. 
     The potential difference detection unit  23  detects a potential difference between the electrodes (i.e., potential difference detection electrode) electrically connected to the potential difference detection unit  23  by the terminal switching unit  22 , and outputs the detected potential difference to the control unit  10 . In this manner, the potential difference between the potential difference detection electrodes with the constant current applied to the subject is detected. 
     The physical information measurement unit  24  and the subject information input unit  25  are sites for obtaining subject information used in the calculation process performed in the body fat mass calculating portion  13  of the calculation processing section  11 . The “subject information” refers to information related to the subject, and includes at least one of the information of age, sex, or physical information. The “physical information” includes information related to a size at a specific site of the body of the subject (e.g., information including at least one of abdomen peripheral length (waist length) and abdomen lateral width, abdomen thickness, height, etc.), or information such as a weight. The physical information measurement unit  24  is a unit for automatically measuring the physical information of the subject, and outputs the detected physical information to the control unit  10 . The subject information input unit  25  is a unit for inputting the subject information, and outputs the inputted subject information to the control unit  10 . 
     In the function block diagram shown in  FIG. 1 , a case where both the physical information measurement unit  24  and the subject information input unit  25  are arranged in the body fat measurement device  1 A has been described, but both the physical information measurement unit  24  and the subject information input unit  25  are not essential configurations. Whether or not to arrange the physical information measurement unit  24  and/or subject information input unit  25  is appropriately selected based on the type of subject information used in a calculation process performed in the calculation processing section  11  of the control unit  10 . The physical information of the subject information may be automatically measured using the physical information measurement unit  24 , and the measurement data may be used, or the subject himself/herself may input the information at the subject information input unit  25  without arranging the physical information measurement unit  24  and the input data may be used. 
     The calculation processing section  11  includes the impedance measuring portion  12  and the body fat mass calculating portion  13 , as described above. The impedance measuring portion  12  calculates various types of bioelectrical impedances based on the current value of the constant current generated by the constant current generation unit  21 , and the potential difference information inputted to the control unit  10  detected in the potential difference detection unit  23 . The body fat mass calculating portion  13  calculates the body fat mass based on the bioelectrical impedance obtained by the impedance measuring portion  12  and the subject information inputted from the physical information measurement unit  24  and/or the subject information input unit  25 . The body fat mass calculating portion  13  includes, for example, at least one of a total fat mass calculating part  14  for calculating the body fat mass of the entire body of the subject, a site type fat mass calculating part  15  for calculating the fat mass by specific site of the body of the subject, a visceral fat mass calculating part  16  for calculating the visceral fat mass of the subject, and a subcutaneous fat mass calculating part  17  for calculating the subcutaneous fat mass at the abdomen of the subject. 
     The display unit  26  displays information of various types of body fat mass calculated by the body fat mass calculating portion  13 . An LCD (Liquid Crystal Display), and the like can be used for the display unit  26 . The fat mass displayed on the display unit  26  may be total fat mass, i.e., the fat mass of the entire body of the subject, the site type fat mass, i.e., the fat mass of specific site of the body of the subject, the visceral fat mass, the subcutaneous fat mass at the abdomen, and the like. The “fat mass” refers to an index indicating the fat mass represented by a weight of fat, area of fat, volume of fat, fat level, and the like. In particular, the “visceral fat mass” refers to an index represented by at least one of a weight of visceral fat, area of visceral fat, volume of visceral fat, and visceral fat level; and the “subcutaneous fat mass” refers to an index represented by at least one of a weight of subcutaneous fat, area of subcutaneous fat, volume of subcutaneous fat, and subcutaneous fat level. 
     The operation unit  27  is a unit for the subject to input a command to the body fat measurement device  1 A, and is configured by a key and the like that can be pushed by the subject. 
     The power supply unit  28  is a unit for supplying power to the control unit  10 , and includes an internal power supply such as a battery and an external power supply such as a commercial power supply. 
     The memory  29  is a unit for storing various types of data and program related to the body fat measurement device  1 A, and stores the subject information, the various types of calculated body fat mass, body fat measurement program for executing the body fat measurement process described below, and the like. 
     One example of the calculation process performed in the body fat measurement device  1 A according to the present embodiment will now be described. As described above, various types of body fat mass can be measured by the body fat mass calculating portion  13  in the body fat measurement device  1 A according to the present embodiment, where particularly described below by way of example is the calculation process performed when calculating the area of the visceral fat serving as an index indicating the visceral fat mass, the area of the subcutaneous fat serving as an index indicating the subcutaneous fat mass, and the body fat percentage serving as an index indicating the relationship of the body fat mass and the weight. 
     With reference to  FIG. 1 , the impedance measuring portion  12  calculates two types of bioelectrical impedances based on the current value of the constant current generated by the constant current generation unit  21  and the potential difference detected by the potential difference detection unit  23 . One of the two types of bioelectrical impedances is a bioelectrical impedance Zt reflecting the fat free mass at the abdomen of the subject. The other bioelectrical impedance is a bioelectrical impedance Zs reflecting the subcutaneous fat mass at the abdomen of the subject. 
     The visceral fat mass calculating part  16  calculates a visceral fat area Sv (unit: cm 2 ) of the subject based on the calculated two types of impedances Zt, Zs, and a waist length W, which is one of the physical information of the subject. Specifically, the visceral fat area Sv is calculated by the following equation (1) expressing the relationship of the two types of impedances Zt, Zs and the waist length W of the subject, and the visceral fat area Sv. 
         Sv=a×W   2   −b× (1 /Zt )− c×W×Zs−d    (1) 
     (where, a, b, c, d: coefficient) 
     The subcutaneous fat mass calculating part  17  calculates a subcutaneous fat area Ss (unit: cm 2 ) of the subject based on the calculated bioelectrical impedance Zs and the waist length W, which is one of the physical information of the subject. Specifically, the subcutaneous fat area Ss is calculated by the following equation (2) expressing the relationship of the bioelectrical impedance Zs and the waist length W of the subject, and the subcutaneous fat area Ss. 
         Ss=e×W×Zs+f    (2) 
     (where, e, f: coefficients) 
     The total fat mass calculating part  14  calculates a fat free mass FFM (unit: kg) based on the calculated bioelectrical impedance Zt and a height H, which is one of the physical information of the subject. Specifically, the fat free mass FFM is calculated by the following equation (3) expressing the relationship of the bioelectrical impedance Zt and the height H of the subject, and the fat free mass FFM. 
         FFM=i×H   2   /Zt+j    (3) 
     (where i, j: coefficients) 
     The coefficients in each equation (1), (2), and (3) as above are defined by a regression equation based on the measurement result of an MRI. The coefficients in each equation (1), (2), and (3) may be defined by age and/or sex. 
     The total fat mass calculating part  14  calculates the body fat mass of the subject such as body fat percentage (%) based on the calculated fat free mass FFM and the weight Wt, which is physical information, when calculating the body fat mass of the entire body of the subject, although not directly related to the calculation of the visceral fat area Sv or the calculation of the subcutaneous fat area Ss. Specifically, for example, the body fat percentage is calculated by the following equation (4) based on the fat free mass FFM and the weight Wt of the subject. 
       Body fat percentage=( Wt−FFM )/ Wt× 100   (4) 
     Although the specific description will not be given, the body fat mass by sites of the body can be calculated based on the bioelectrical impedance, obtained by variously switching the current application electrode and the potential difference detection electrode, and the physical information of the subject. 
       FIG. 2  is a flowchart showing the operation procedures of the body fat measurement device in measuring the visceral fat area, the subcutaneous fat area, and the body fat percentage using the body fat measurement device according to the present embodiment. The operation of the body fat measurement device  1 A in measuring the visceral fat area, the subcutaneous fat area, and the body fat percentage using the body fat measurement device  1 A will be described with reference to  FIG. 2 . 
     The process shown in the flowchart of  FIG. 2  is stored in the memory  29  as a program in advance, where the control unit  10  including the calculation processing section  11  reads out and executes the program to realize the functions of the visceral fat area measurement process, the subcutaneous fat area measurement process, and the body fat percentage measurement process. The operation procedures described below are the operation procedures in the case where four sets of abdominal electrode groups, each set including four abdominal electrodes A 11 , A 12 , A 21 , A 22  shown in the figure, are arranged parallel to each other in the body fat measurement device shown in  FIG. 1 . 
     With reference to  FIG. 2 , the control unit  10  accepts the input of the subject information containing the waist length W, the height H, the weight Wt and the like serving as physical information (step S 1 ). The accepted subject information is temporarily saved in the memory  29 , for example. If a configuration of automatically measuring specific physical information of the subject information using the physical information measurement unit  24  is adopted, the physical information measured by the physical information measurement unit  24  is inputted to the control unit  10 . 
     The control unit  10  determines whether or not an instruction to start the measurement is made (step S 2 ). The control unit  10  waits until the instruction to start the measurement is made (NO in step S 2 ). The control unit  10  sets the electrode (step S 3 ) when detecting the instruction to start the measurement (YES in step S 2 ). 
     In step S 3 , the control unit  10  selects, for example, a pair of upper limb electrode H 11  and lower limb electrode F 11  and a pair of upper limb electrode H 21  and lower limb electrode F 21  as the current application electrode pairs, and selects one pair of abdominal electrodes A 11 , A 21  in one abdominal electrode group of the four sets of abdominal electrode groups as the potential difference detection electrode pair. The terminal switching unit  22  electrically connects the pair of upper limb electrode H 11  and lower limb electrode F 11  and the pair of upper limb electrode H 21  and lower limb electrode F 21  with the constant current generation unit  21 , and electrically connects the pair of abdominal electrodes A 11 , A 21  with the potential difference detection unit  23  based on the control of the control unit  10 . In this case, the terminal switching unit  22  cuts the electrical connection of the non-selected electrode and the constant current generation unit  21  and the potential difference detection unit  23  based on the control of the control unit  10 . 
     The constant current generation unit  21  flows a constant current between the upper limb and the lower limb based on the control of the control unit  10 . For instance, the constant current generation unit  21  flows a constant current from the upper limb electrode H 11  and the upper limb electrode H 21  to the lower limb electrode F 11  and the lower limb electrode F 21  (step S 4 ). In this case, the terminal switching unit  22  preferably has a configuration of short circuiting the upper limb electrode H 11  and the upper limb electrode H 21  and short circuiting the lower limb electrode F 11  and the lower limb electrode F 21 . The constant current generation unit  21  and the terminal switching unit  22  may have a configuration of flowing a constant current from either one of the upper limb electrodes H 11 , H 21  to either one of the lower limb electrodes F 11 , F 21 . 
     In this state, the potential difference detection unit  23  detects the potential difference between the abdominal electrodes A 11 , A 21  based on the control of the control unit  10  (step S 5 ). 
     The control unit  10  determines whether or not the detection of the potential difference is completed for the combinations of all electrode pairs defined in advance (step S 6 ). The control unit  10  proceeds to step S 3  when determined that the detection of the potential difference is not completed for the combination of all of the electrode pairs defined in advance (NO in step S 6 ). The control unit  10  proceeds to step S 7 , to be hereinafter described, when determined that the detection of the potential difference is completed for the combination of all of the electrode pairs defined in advance (YES in step S 6 ). 
     In this manner, the control unit  10  selects the abdominal electrodes A 11 , A 21  of another abdominal electrode group in order as the potential difference detection electrode pair. That is, the terminal switching unit  22  electrically connects the abdominal electrodes A 11 , A 21  of another abdominal electrode group with the potential difference detection unit  23  in order based on the control of the control unit  10  (step S 3 ). The potential difference detection unit  23  then detects the potential difference between the abdominal electrodes A 11 , A 21  of another abdominal electrode group in order based on the control of the control unit  10  (step S 5 ). 
     When the detection of the potential difference is completed for the combination of the abdominal electrodes A 11 , A 21  in all of the abdominal electrode groups (YES in step S 6 ), the impedance measuring portion  12  calculates the bioelectrical impedances Zt1 to Zt4 based on the current value of the constant current generated by the constant current generation unit  21  and flowed through the body and each potential difference detected by the potential difference detection unit  23  (step S 7 ). The values of the bioelectrical impedances Zt1 to Zt4 calculated by the impedance measuring portion  12  are temporarily saved in the memory  29 , for example. 
     The control unit  10  then sets the electrodes again (step S 8 ). More specifically, the control unit  10  selects the pair of abdominal electrodes A 11 , A 21  in one abdominal electrode group of the four sets of abdominal electrode groups as the current application electrode pair, and selects the pair of abdominal electrodes A 12 , A 22  in the abdominal electrode group as the potential difference detection electrode pair. The terminal switching unit  22  electrically connects the pair of abdominal electrodes A 11 , A 21  with the constant current generation unit  21  and electrically connects the pair of abdominal electrodes A 12 , A 22  with the potential difference detection unit  23  based on the control of the control unit  10 . In this case, the terminal switching unit  22  cuts the electrical connection of the non-selected abdominal electrode, the upper limb electrode and the lower limb electrode and the constant current generation unit  21  and the potential difference detection unit  23  based on the control of the control unit  10 . 
     The constant current generation unit  21  flows a constant current between the abdominal electrodes A 12 , A 22  based on the control of the control unit  10  (step S 9 ). 
     In this state, the potential difference detection unit  23  detects the potential difference between the abdominal electrodes A 21 , A 21  based on the control of the control unit  10  (step S 10 ). 
     The control unit  10  then determines whether or not the detection of the potential difference is completed for the combinations of all electrode pairs defined in advance (step S 11 ). The control unit  10  proceeds to step S 8  when determined that the detection of the potential difference is not completed for the combination of all of the electrode pairs defined in advance (NO in step S 11 ). The control unit  10  proceeds to step S 12 , to be hereinafter described, when determined that the detection of the potential difference is completed for the combination of all of the electrode pairs defined in advance (YES in step S 11 ). 
     In this manner, the control unit  10  selects the abdominal electrodes A 11 , A 21  of another abdominal electrode group as the current application electrode pair, and selects the abdominal electrodes A 12 , A 22  in the relevant abdominal electrode group in order as the potential difference detection electrode pair. In other words, the terminal switching unit  22  electrically connects the abdominal electrodes A 11 , A 21  of another abdominal electrode group with the constant current generation unit  21  in order, and electrically connects the abdominal electrodes A 12 , A 22  in the relevant abdominal electrode group with the potential difference detection unit  23  in order based on the control of the control unit  10  (step S 8 ). The potential difference detection unit  23  then flows a constant current between the abdominal electrodes A 11 , A 12  in another abdominal electrode group (step S 9 ), and detects the potential difference between the abdominal electrodes A 12 , A 22  in the relevant abdominal electrode group in order based on the control of the control unit  10  (step S 10 ). 
     When the application of the current and the detection of the potential difference for the combination of the electrode pairs in all of the abdominal electrode groups are completed (YES in step S 11 ), the impedance measuring portion  12  calculates bioelectrical impedances Zs1 to Zs4 (step S 12 ) based on the current value of the constant current generated by the constant current generation unit  21  and flowed through the body and each potential difference detected by the potential difference detection unit  23 . The values of the bioelectrical impedances Zs1 to Zs4 calculated by the impedance measuring portion  12  are temporarily saved in the memory  29 , for example. 
     The visceral fat mass calculating part  16  then calculates the visceral fat area Sv based on the waist length W of the physical information accepted by the control unit  10  in step S 1 , the calculated bioelectrical impedances Zt1 to Zt4, and the bioelectrical impedances Zs1 to Zs4 (step S 13 ). The visceral fat area Sv is calculated by equation (1). In the case where four sets of abdominal electrode groups, each set including four abdominal electrodes A 11 , A 12 , A 21 , A 22 , are arranged parallel to each other, the average value of the four bioelectrical impedances Zt1 to Zt4 and the average value of the four bioelectrical impedances Zs1 to Zs4, for example, are respectively substituted to equation (1). 
     The subcutaneous fat mass calculating part  17  then calculates the subcutaneous fat area Ss based on the waist length W of the physical information accepted by the control unit  10  in step S 1 , and the calculated bioelectrical impedances Zs1 to Zs4 (step S 14 ). The subcutaneous fat area Ss is calculated by substituting the waist length W and the calculated bioelectrical impedance Zs to equation (2). In the case where four sets of abdominal electrode groups, each set including four abdominal electrodes A 11 , A 12 , A 21 , A 22 , are arranged parallel to each other, the average value of the four bioelectrical impedances Zs1 to Zs4 is substituted to the bioelectrical impedance Zs of equation (2). 
     The total fat mass calculating part  14  calculates the fat free mass FFM based on the height H of the physical information accepted by the control unit  10  in step S 1  and the calculated bioelectrical impedance Zt (step S 15 ). The fat free mass FFM is calculated by equation (3). 
     The total fat mass calculating part  14  calculates the body fat percentage based on the weight Wt of the physical information accepted by the control unit  10  in step S 1 , and the fat free mass FFM calculated by the total fat mass calculating part  14  in step S 15  (step S 16 ). The body fat percentage is calculated from equation (4). 
     The display unit  26  displays each measurement result based on the control of the control unit  10  (step S 17 ). 
     The body fat measurement device  1 A then ends the body fat mass measurement process including the visceral fat area measurement process, the subcutaneous fat area measurement process, and the body fat percentage measurement process. A typical value of the bioelectrical impedances Zt1 to Zt4 is about 5 Ω. A typical value of the bioelectrical impedances Zs1 to Zs4 is about 80 Ω. 
       FIG. 3  is a view showing an outer appearance structure of the body fat measurement device according to the present embodiment, and is a perspective view showing a state where various types of attachment units arranged in the body fat measurement device are attached to the subject. The outer appearance structure of the body fat measurement device  1 A according to the present embodiment and a posture to be taken by the subject in measurement will be described with reference to  FIG. 3 . The body fat measurement device  1 A described below is configured with four sets of abdominal electrode groups, each set including four illustrated abdominal electrodes A 11 , A 12 , A 21 , A 22 , arranged parallel to each other in the body fat measurement device shown in  FIG. 1 . 
     As shown in  FIG. 3 , the body fat measurement device  1 A according to the present embodiment includes a bioelectrical impedance measurement abdomen attachment unit (bioelectrical impedance measurement abdomen attachment unit according to the present embodiment)  100 A to be attached to an abdomen  301  of a subject  300 , a pair of bioelectrical impedance measurement upper limb attachment units  172 A,  172 B to be attached to the upper limb of the subject  300 , a pair of bioelectrical impedance measurement lower limb attachment units  173 A,  173 B to be attached to the lower limb of the subject  300 , and a device main body  165  connected to the various types of attachment units  100 A,  172 A,  172 B,  173 A,  173 B by way of a connection cable  180 . 
     The bioelectrical impedance measurement abdomen attachment unit  100 A is configured by a band-shaped member that can be wrapped around the abdomen  301 . Each of the bioelectrical impedance measurement upper limb attachment units  172 A,  172 B and the bioelectrical impedance measurement lower limb attachment units  173 A,  173 B is configured by a clip-shaped member capable of sandwiching the upper limb or the lower limb of the subject  300 . The bioelectrical impedance measurement abdomen attachment unit  100 A includes abdominal electrodes (abdominal electrodes A 11 , A 12 , A 21 , A 22  described above) capable of being arranged in contact with the surface of the abdomen of the subject. Each bioelectrical impedance measurement upper limb attachment unit  172 A,  172 B includes an upper limb electrode (upper limb electrodes H 11 , H 12 , H 21 , H 22  described above) capable of being arranged in contact with the surface of the upper limb of the subject. Each bioelectrical impedance measurement lower limb attachment unit  173 A,  173 B includes a lower limb electrode (lower limb electrodes F 11 , F 12 , F 21 , F 22  described above) capable of being arranged in contact with the surface of the lower limb of the subject. The specific configuration of the bioelectrical impedance measurement abdomen attachment unit  100 A according to the present embodiment will be described below. 
     The device main body  165  includes the control unit  10 , the constant current generation unit  21 , the terminal switching unit  22 , the potential difference detection unit  23 , the subject information input unit  25 , the display unit  26 , the operation unit  27 , the memory  29 , and the like. The constant current generation unit  21 , the terminal switching unit  22 , the potential difference detection unit  23 , and the like arranged in the device main body  165  may be arranged in the bioelectrical impedance measurement abdomen attachment unit  100 A, as necessary. 
     As shown in  FIG. 3 , when measuring various types of body fat mass, the subject  300  take a laid position (i.e., posture of lying with face up) on a bed surface  400 . The bioelectrical impedance measurement abdomen attachment unit  100 A is attached to the abdomen  301  of the subject  300 , the bioelectrical impedance measurement upper limb attachment units  172 A,  172 B are attached to the upper limb (suitably, wrists  302 A,  302 B) of the subject  300 , and the bioelectrical impedance measurement lower limb attachment units  173 A,  173 B are attached to the lower limb (suitably, ankles  303 A,  303 B) of the subject  300 . The electrodes arranged at the various types of attachment units  100 A,  172 A,  1728 ,  173 A,  173 B are brought into contact with the body surface of the subject  300  by attaching the various types of attachment units  100 A,  172 A,  172 B,  173 A,  173 B. The subject  300  maintains the laid position during the measurement of various types of body fat mass. 
       FIGS. 4 and 5  are views showing an outer appearance structure of the bioelectrical impedance measurement abdomen attachment unit according to the present embodiment, where  FIG. 4  is a perspective view and  FIG. 5  is a bottom view.  FIG. 6  is a cross-sectional view taken along line VI-VI shown in  FIGS. 4 and 5  of the bioelectrical impedance measurement abdomen attachment unit according to the present embodiment. The structure of the bioelectrical impedance abdomen attachment unit  100 A according to the present embodiment will be described in detail with reference to  FIGS. 4 to 6 . 
     As shown in  FIGS. 4 and 5 , the bioelectrical impedance measurement abdomen attachment unit  100 A according to the present embodiment mainly includes an electrode support  110  and a belt  140 . The electrode support  110  includes a sheet-like portion  111  including a sheet-like member having a substantially rectangular shape in plan view, an electrode support mechanism accommodating portion  112  arranged on an upper surface of the sheet-like portion  111 , a plurality of electrodes  113  arranged so as to be partially exposed at the lower surface of the sheet-like portion  111 , a fixing portion  114  arranged at one end in a length direction of the sheet-like portion  111 , and a holder  115  arranged at the other end in the length direction of the sheet-like portion  111 . 
     As shown in  FIG. 4 , one end  141  of the belt  140  is fixed so as to be relatively immovable with respect to the electrode support  110  by the fixing portion  114 . The belt  140  is fixed with respect to the electrode support  110  by sandwiching the one end  141  of the belt  140  with the sheet-like portion  111  and a plate-shaped member which is screw fixed or the like to the sheet-like portion  111 . The electrode support  110  and the belt  140  thereby configure the band-shaped member to be wrapped around the abdomen of the subject. 
     The sheet-like portion  111  is configured by a member that substantially does not have stretchability, and is made of a flexible material so as to fit to the surface of the abdomen of the subject in the attached state. The belt  140  has a long shape with a narrow width compared to the sheet-like portion  111 , and is configured by a member that substantially does not have stretchability in the length direction. The belt  140  is configured by a belt with teeth (timing belt) having teeth formed on one surface (main surface on the side not facing the abdomen of the subject in the attached state). The belt  140  is made of a flexible material so as to fit to the surface of the abdomen of the subject in the attached state. 
     As shown in  FIG. 6 , each of the plurality of electrodes  113  arranged in the electrode support  110  includes a rod portion  113   a  that extends in a rod-shape, and a plate-shaped portion  113   b  arranged at the distal end of the rod portion  113   a.  The rod portion  113   a  is inserted to an insertion hole formed in the sheet-like portion  111 . The plate-shaped portion  113   b  is exposed at the lower surface side of the sheet-like portion  111 . The main surface on the side not coupled to the rod portion  113   a  of the plate-shaped portion  113   b  becomes the contacting surface that comes into contact with the abdomen of the subject. Each of the plurality of electrodes  113  is made of metal material excelling in biocompatibility. The plurality of electrodes  113  are arranged in a matrix form at the lower surface of the electrode support  110 , where each of the electrodes  113  respectively corresponds to the abdominal electrodes A 11 , A 12 , A 21 , A 22 . 
     With reference to  FIG. 4 , the electrode support mechanism accommodating portion  112  is configured by a member having a box-shape, and interiorly includes an electrode support mechanism for movably supporting each of the plurality of electrodes  113  in a specific direction. The electrode support mechanism accommodating portion  112  is arranged for each of the four sets of abdominal electrode groups, where each set includes the abdominal electrodes A 11 , A 12 , A 21 , A 22 . 
     As shown in  FIG. 6 , the electrode support mechanism arranged in the interior of the electrode support mechanism accommodating portion  112  is configured by a guide frame  116  having a base body  116   a  fixed to the sheet-like portion  111  and a lid body  116   b  fixed to the base body  116   a  by a screw and the like, and a coil spring  117  arranged in a space formed in the interior of the guide frame  116 . Each of the base body  116   a  and the lid body  116   b  configuring the guide frame  116  has an insertion hole, where the rod portion  113   a  of the electrode  113  is inserted and arranged in a hollow part of the coil spring  117  by inserting the rod portion  113   a  of the electrode  113  to the insertion hole. The coil spring  117  has one end in contact with the lid body  116   b,  and the other end in contact with a collar portion  113   a   1  formed at the rod portion  113   a  of the electrode  113 . With this configuration, the plurality of electrodes  113  are thereby movably supported by the electrode support mechanism so as to be movable only in a direction substantially perpendicular to the surface of the abdomen of the subject in the attached state and biased towards the abdomen side by the biasing force of the coil spring  117 . 
     As shown in  FIG. 4 , the holder  115  arranged at the other end in the length direction of the sheet-like portion  111  (end on the side not arranged with the fixing portion  114 ) includes a belt feeding portion  120  and an attachment portion  130 . The belt feeding portion  120  and the attachment portion  130  both have an insertion path through which the belt  140  is inserted at the predetermined position. The belt feeding portion  120  is fixed to the sheet-like portion  111 , and holds the inserted belt  140  in a manner enabling entering and exiting. The attachment portion  130  interiorly includes a fixing mechanism (details to be described below) that can be fixedly attached to an arbitrary position of the belt  140  inserted to the attachment portion  130  so as to be removably attached to an arbitrary position of the belt  140 . The holder  115  serves to hold the portion closer to the other end  142  of the belt  140  so as to be relatively movable with respect to the electrode support  110  in the attached state, where the detailed configurations and functions will be described below. 
     As shown in  FIG. 4 , a connector  118  for attaching the connection cable  180  for relaying various types of attachment units and the device main body is formed at the predetermined position of the sheet-like portion  111 . As shown in  FIG. 5 , a positioning through-hole  119  aligned at an umbilicus position of the subject to position the electrode  113  with respect to the abdomen at the time of attachment is formed substantially at the central part of the sheet-like portion  111 . 
       FIG. 7  is a schematic cross-sectional view showing a state where the bioelectrical impedance measurement abdomen attachment unit according to the present embodiment is attached to the abdomen of the subject. The state where the bioelectrical impedance measurement abdomen attachment unit  110 A according to the present embodiment is attached to the abdomen of the subject will be described with reference to  FIG. 7 . 
     As shown in  FIG. 7 , in the state where the bioelectrical impedance measurement abdomen attachment unit  100 A according to the present embodiment is attached to the abdomen  301  of the subject  300 , the bioelectrical impedance measurement abdomen attachment unit  100 A including a band-shaped member is attached in a wrapped-around state to the abdomen  301  of the subject  300 . At the time of attachment, the electrode support  110  is positioned and placed on the abdomen  301  of the subject so that the positioning through-hole  119  formed in the electrode support  110  matches the umbilicus position of the subject  300 , and the belt  140  is wrapped around the flank and the rear surface of the abdomen of the subject  300  in the positioned state. The bioelectrical impedance measurement abdomen attachment unit  100 A is attached to the abdomen  301  of the subject  300  by holding the portion closer to the other end  142  of the belt  140  with the holder  115  arranged at the electrode support  110 . In this manner, the plurality of electrodes  113  arranged on the lower surface side (inner peripheral surface side in the attached state) of the electrode support  110  are arranged in contact with the front surface of the abdomen of the subject  300 . 
       FIGS. 8A and 8B  are perspective views describing a detailed structure of the holder of the bioelectrical impedance measurement abdomen attachment unit according to the present embodiment.  FIG. 9  is a schematic view showing an internal structure of the attachment portion of the holder. The detailed structure of the holder of the bioelectrical impedance measurement abdomen attachment unit  100 A according to the present embodiment and a mechanism of holding the belt with the holder will be described below with reference to  FIGS. 8A ,  8 B, and  9 . In  FIGS. 8A ,  8 B, and  9 , the illustration of a casing will be partially or entirely omitted for both the belt feeding portion and the attachment portion to facilitate understanding. 
     As shown in  FIGS. 8A and 8B , the belt feeding portion  120  arranged at the sheet-like portion  111  of the electrode support  110  interiorly includes a pulley with teeth  121 . The pulley with teeth  121  is rotatably supported while facing an insertion path formed in the belt feeding portion  120 , and gears with the teeth of the belt  140  inserted through the insertion path. A hook  122  formed to an anchor shape is arranged on the outer surface of the belt feeding portion  120 . 
     As shown in  FIGS. 8A ,  8 B, and  9 , the attachment portion  130  removably attached to the belt  140  mainly includes a band winding mechanism  131  and a fixing mechanism  136 . 
     The band winding mechanism  131  is a mechanism corresponding to a biasing portion for biasing the attachment portion  130  and the belt feeding portion  120  in an approaching direction in the attached state. Specifically, as shown in  FIGS. 8A ,  8 B, and  9 , the band winding mechanism  131  mainly include a reel body  132 , a band  133 , and a protrusion spring  134   a  accommodated in a spring accommodating portion  134 . The reel body  132  is rotatably supported in the attachment portion  130 . The band  133  is made of a non-stretchable long band-shaped member, having one end fixed to the reel body  132  and being wound to the reel body  132 . The protrusion spring  134   a  serving as the spring member is accommodated in the spring accommodating portion  134 , where one end of the protrusion spring  134   a  is fixed to the casing of the spring accommodating portion  134  and the other end is fixed to a rotation shaft of the reel body  132 . 
     The reel body  132 , the band  133 , and the protrusion spring  134   a  configure the band winding mechanism  131 . With this configuration, the band  133  is drawable from the reel body  132 , and the band  133  is wound up by the reel body  132  by an elastic force of the protrusion spring  134   a  that functions as an elastic force expressing member in a state where a force is not applied to the band  133 . A buckle  135  is attached to the end of the band  133  on the side not fixed to the reel body  132 . The buckle  135  includes a locking hole that can engage the hook  122  arranged at the belt feeding portion  120 . 
     As described above, the fixing mechanism  136  is a mechanism for fixedly attaching the attachment portion  130  to an arbitrary position of the belt  140 . Specifically, as shown in  FIGS. 8A ,  8 B, and  9 , the fixing mechanism  136  is mainly configured by a push button  137 , a relay member  138  that moves up and down in conjunction with the push button  137 , a turning lock member  139  arranged so that one end comes into contact with the relay member  138 , and a spring  138   a  for biasing the relay member. A locking nail  139   a  that can gear with the teeth formed on the surface of the belt  140  is arranged at the distal end of the turning lock member  139 . The turning lock member  139  turns, with the operation controlled by the relay member  138  that moves up and down in conjunction with the operation of the push button  137 , and fixedly attaches the attachment portion  130  to an arbitrary position of the belt  140  by having the locking nail  139   a  arranged at the distal end by gearing with or not gearing with the teeth of the belt  140 . 
     The task procedure for having the holder arranged at the electrode support hold the portion closer to the other end of the belt will be described below with reference to  FIGS. 8A and 8B . The task procedure described below is performed after wrapping the bioelectrical impedance measurement abdomen attachment unit  100 A to the abdomen of the subject, and the attached state shown in  FIGS. 3 and 7  is achieved only after going through the task procedures. 
     In order to hold the portion closer to the other end  142  of the belt  140  with the holder  115 , the other end  142  of the belt  140  inserted to the insertion path of the attachment portion  130  in advance is first inserted to the insertion path of the belt feeding portion  120  in a direction of an arrow A in the figure, as shown in  FIG. 8A . In this manner, the teeth formed at the inserted belt  140  gears with the teeth of the pulley with teeth  121  arranged at the belt feeding portion  120 . 
     The attachment portion  130  attached so as to be movable with respect to the belt  140  in advance is then fixedly attached to a predetermined position of the belt  140  using the fixing mechanism  136 , as shown in  FIG. 8A . In this case, the position of the attachment portion  130  is adjusted in a direction of an arrow B in the figure, where the attachment position is a position spaced apart by a sufficient distance with respect to the belt feeding portion  120 . 
     The band  133  arranged at the attachment portion  130  is then pulled out in a direction of an arrow C in the figure, and the buckle  135  attached at the distal end of the band  133  is locked with the hook  122  arranged at the belt feeding portion  120 , as shown in  FIG. 8B . The locking is carried out by hooking the locking hole formed in the buckle  135  to the anchor-shaped hook  122 . 
     Through the above task procedures, the holding of the portion closer to the other end  142  of the belt  140  by the holder  115  is completed. In the attached state realized through the above-described task procedures, the portion closer to the other end  142  of the belt  140  is fixed to the electrode support  110  by way of the attachment portion  130  fixedly attached to the predetermined position of the belt  140  and the belt feeding portion  120  elastically connected to the attachment portion  130 . 
     In the attached state, the waist length of the subject increases when the subject performs the inhaling motion, and the band  133  is accordingly pulled out from the reel body  132  against the biasing force of the protrusion spring  134   a  serving as the elastic force expressing member. Accompanied therewith, the belt  140  is fed in the direction of an arrow D 1  shown in  FIG. 8B  from the belt feeding portion  120 , whereby the distance between the attachment portion  130  and the belt feeding portion  120  increases thereby increasing the wrapping length of the belt  140  with respect to the abdomen of the subject. 
     When the subject performs the exhaling motion, on the other hand, the waist length of the subject decreases, and the band  133  is accordingly wound up by the reel body  132  by the biasing force of the protrusion spring  134   a  serving as the elastic force expressing member. Accompanied therewith, the belt  140  is fed in the direction of an arrow D 2  shown in  FIG. 8B  from the belt feeding portion  120 , whereby the distance between the attachment portion  130  and the belt feeding portion  120  decreases thereby decreasing the wrapping length of the belt  140  with respect to the abdomen of the subject. 
     According to the configuration of the bioelectrical impedance measurement abdomen attachment unit  100 A according to the present embodiment described above, the attachment portion  130  attached to an arbitrary position of the portion closer to the other end  142  of the belt  140  and the belt feeding portion  120  arranged at the electrode support  110  are coupled by a winding device serving as a biasing portion including the protrusion spring  134   a  arranged in the attachment portion  130  in the attached state. Therefore, the portion closer to the other end  142  of the belt  140  is constantly pulled towards the belt feeding portion  120  side (i.e., electrode support  110  side) based on the biasing force of the winding device (i.e., elastic force of protrusion spring  134   a ). Therefore, the abdomen  301  of the subject  300  is tightened with a substantially constant tightening strength by the bioelectrical impedance abdomen attachment unit  100 A based on the biasing force of the protrusion spring  134   a,  whereby the plurality of electrodes  113  can be pressed against the abdomen  301  of the subject  300  with a substantially constant load. The tensile load applied on the band-shaped member including the sheet-like portion  111  and the belt  140  when the pressing force of the electrode  113  with respect to the abdomen  301  of the subject  300  is optimized is approximately about 1.0 kgf to 2.0 kgf, and preferably 1.5 kgf. 
     Through the use of the above-described configuration, the attachment portion  130  can be attached to an arbitrary position of the portion closer to the other end  142  of the belt  140 , and thus the bioelectrical impedance measurement abdomen attachment unit  100 A can be closely attached to the abdomen  301  of the subject  300  with satisfactory reproducibility regardless of the waist length of the subject  300  by attaching the attachment portion  130  to an appropriate position of the belt  140 . 
     Furthermore, through the use of the above-described configuration, the wrapping length of the bioelectrical impedance measurement abdomen attachment unit  100 A changes following the breathing motion of the subject  300  by appropriately adjusting the biasing force of the winding device (i.e., elastic force of protrusion spring  134   a ), and thus the excessive oppressing feeling is not felt by the subject  300 , and the bioelectrical impedance measurement abdomen attachment unit that is not painful to the subject  300  is realized. 
     Therefore, the bioelectrical impedance measurement attachment unit which enables the electrode to be pressed against the body of the subject with a constant load in the attached state and which is not painful to the subject is realized with the bioelectrical impedance measurement abdomen attachment unit  100 A according to the present embodiment. The body fat measurement device capable of calculating the body fat mass at high accuracy is realized with the body fat measurement device  1 A equipped with the bioelectrical impedance measurement abdomen attachment unit  100 A. 
     Second Embodiment 
       FIG. 10  is a view showing function blocks of a body fat measurement device according to a second embodiment of the present invention. First, a configuration of function blocks of a body fat measurement device  1 B according to the present embodiment will be described with reference to  FIG. 10 . The same reference numerals are denoted for the portions similar to the first embodiment, and the description thereof will not be repeated herein. 
     As shown in  FIG. 10 , the body fat measurement device  1 B according to the present embodiment includes a waist length measurement unit  30  serving as a physical information measurement unit. The waist length measurement unit  30  is a unit for automatically measuring the waist length of the subject, and measures the waist length of the subject based on the output of various sensors arranged in the bioelectrical impedance measurement abdomen attachment unit (bioelectrical impedance measurement abdomen attachment unit according to the present embodiment)  100 B. The waist length of the subject constantly fluctuates, although slightly, with the breathing motion. The waist length measurement unit  30  constantly measures the fluctuating waist length during the measurement, and measures the waist length of the subject by detecting the wrapping length of the belt wrapped around the body of the subject and also measures the fluctuation of the waist length of the subject by detecting the fluctuation of the wrapping length of the belt wrapped around the body of the subject. The waist length measurement unit  30  outputs the information of the measured waist length and the information of the fluctuation thereof to the control unit  10 . The waist length is the body peripheral length of the portion including the umbilicus position of the subject. In other words, the waist length measurement unit  30  functions as a body peripheral length measurement unit and also functions as a body peripheral length fluctuation amount measurement unit. 
     In the body fat measurement device  1 B according to the present embodiment, the calculation processing section  11  includes a breathing state detecting portion  18  in addition to the impedance measuring portion  12  and the body fat mass calculating portion  13 . The breathing state detecting portion  18  detects the breathing state of the subject during the measurement operation based on the information of the waist length of the subject measured by the waist length measurement unit  30  and inputted to the control unit  10 . The body fat mass calculating portion  13  calculates the body fat mass based on the bioelectrical impedance obtained in the impedance measuring portion  12 , the information of the breathing state obtained in the breathing state detecting portion  18 , and the subject information inputted from the physical information measurement unit  24  and/or the subject information input unit  25 . 
       FIG. 11  is a function block diagram showing a specific configuration of the waist length measurement unit of the body fat measurement device according to the present embodiment.  FIG. 12  is a bottom view of the belt of the bioelectrical impedance measurement abdomen attachment unit according to the present embodiment, and  FIG. 13  is a perspective view showing a structure of a holder. Furthermore,  FIG. 14  is a schematic cross-sectional view of the belt feeding portion of the holder shown in  FIG. 13 . The specific configuration of the waist length measurement unit according to the present embodiment will be specifically described with reference to  FIGS. 11 to 14 . The same reference numerals are denoted for the portions similar to the first embodiment, and the description thereof will not be repeated. 
     As shown in  FIG. 11 , the waist length measurement unit  30  includes a photoelectronic sensor  124  and a rotary encoder  125  serving as a sensor for detecting the position of the belt  140  of the bioelectrical impedance measurement abdomen attachment unit  100 B, and a waist length measurement circuit  151 . Each of the photoelectronic sensor  124  and the rotary encoder  125  is arranged in the belt feeding portion  120  fixed to the electrode support  110  of the holder  115  of the bioelectrical impedance abdomen attachment unit  100 B. Specifically, as shown in  FIG. 14 , the photoelectronic sensor  124  is arranged on the bottom surface of the casing of the belt feeding portion  120  fixed on the electrode support  110  side, where the belt  140  passes the upper side thereof. As shown in  FIGS. 13 and 14 , the rotary encoder  125  is arranged in the belt feeding portion  120  such that a detection shaft  126  is fixed to the pulley with teeth  121  of the belt feeding portion  120 . 
     As shown in  FIG. 12 , an encoder strip  144  is attached to the lower surface of the belt  140  (main surface on the side facing the abdomen of the subject in the attached state, and the surface on the side not formed with teeth). The encoder strip  144  is arranged to extend from the other end  142  of the belt  140  to a predetermined position of the one end  141 , where an identifier (barcode elements  145   a,    145   b,  and the like, herein) indicating an absolute position of the belt  140  is arranged on the surface thereof. The encoder strip  144  is arranged facing the photoelectronic sensor  124 , described above, in the belt feeding portion  120 . 
     The photoelectronic sensor  124  includes a light emitting unit and a light receiving unit, where light emitted from the light emitting unit is applied on the encoder strip  144  and the reflected light is received by the light receiving unit. The photoelectronic sensor  124  outputs an electrical signal by photoelectrically converting the received light, and inputs the same to the waist length measurement circuit  151 . The waist length measurement circuit  151  detects the position of the belt  140  of the portion arranged facing the photoelectronic sensor  124  based on the inputted electrical signal, detects the wrapping length of the belt  140  wrapped around the abdomen of the subject based on the positional information, and specifies the waist length of the subject based thereon. 
     The rotary encoder  125  detects the rotation angle of the pulley with teeth  121  that rotates when the belt  140  is fed out when the detection shaft  126  rotates. The rotary encoder  125  outputs an electrical signal corresponding to the detected rotation angle, and inputs the same to the waist length measurement circuit  151 . The waist length measurement circuit  151  detects the feeding amount of the belt  140  based on the inputted electrical signal, and specifies the fluctuation amount of the wrapping length involved in the breathing motion of the belt  140  wrapped around the abdomen of the subject based thereon. 
     The waist length measurement circuit  151  outputs the waist length and the fluctuation amount of the wrapping length specified using the photoelectronic sensor  124  and the rotary encoder  125  to the control unit  10 . 
     In the present embodiment, the waist length of the subject is specified based on the information detected by the photoelectronic sensor  124 , and the fluctuation amount of the waist length of the subject is specified based on the information detected by the rotary encoder  125 , but the information detected by the rotary encoder  125  may be used to specify the waist length of the subject, and the information detected by the photoelectronic sensor  124  may be used to specify the fluctuation amount of the waist length of the subject. 
     An example of a calculation process carried out in the body fat measurement device  1 B according to the present embodiment will now be described. In the body fat measurement device  1 B according to the present embodiment as well, the calculation process basically the same as the body fat measurement device  1 A according to the first embodiment is carried out, but the value of the waist length actually measured by the waist length measurement unit  30  is used for the value of the waist length W, and the values of the bioelectrical impedances Zt, Zs obtained in association with the information of the breathing state detected by the breathing state detecting portion  18  are used for the values of the bioelectrical impedances Zt, Zs used in various calculation processes. 
     The impedance measuring portion  12  calculates two types of bioelectrical impedances Zt, Zs based on the current value of the constant current generated by the constant current generation unit  21  and the potential difference detected by the potential difference detection unit  23 , but the bioelectrical impedance Zt that reflects the fat free mass at the abdomen of the subject and the bioelectrical impedance Zs that reflects the subcutaneous fat mass at the abdomen of the subject both vary from hour to hour according to the breathing motion of the subject. 
       FIG. 15  is a graph showing a relationship of the fluctuation of the waist length of the subject and the bioelectrical impedance that varies from hour to hour. In  FIG. 15 , a horizontal axis indicates time, where a vertical axis of a portion (A) indicates the waist length and a vertical axis of a portion (B) indicates the bioelectrical impedance. 
     As shown in the portion (A) of  FIG. 15 , the waist length W of the subject fluctuates in accordance with the breathing motion of the subject, where the waist length W increases when the subject performs the inhaling motion and the waist length W decrease when the subject performs the exhaling motion. On the contrary, the bioelectrical impedance Z also fluctuates in accordance with the breathing motion of the subject as shown in the portion (B) of  FIG. 15 , where the value generally decreases when the subject performs the inhaling motion and the value generally increases when the subject performs the exhaling motion. 
     In the body fat measurement device  1 B according to the present embodiment, the following processes are performed on the acquired data to exclude such a fluctuation involved in the breathing motion of the bioelectrical impedance Z as an error component. First, for a predetermined period defined in advance, the potential difference between the potential difference detection electrodes is measured by the potential difference detection unit  23  over a plurality of times at a predetermined interval, and the data of the obtained potential difference is acquired as time-series data. The time-series data of the bioelectrical impedance Z is then obtained from the time-series data of the potential difference obtained by the impedance measuring portion  12 . In parallel thereto, the waist length W of the subject of a period same as the period in which the detection of the potential difference is carried out is acquired as time-series data by the waist length measurement unit  30 . 
     The time-series data of the acquired bioelectrical impedance Z and the time-series data of the waist length W are then synchronized. Thereafter, dW/dt at each time is calculated based on the time-series data of the waist length W in the breathing state detecting portion  18 . If the calculated dW/dt takes a positive value (i.e., dW/dt&gt;0), the subject is determined as performing the exhaling motion (e.g., period of t2 to t3 shown in the portion (A) of  FIG. 15 ), whereas if the calculated dW/dt takes a negative value (i.e., dW/dt&lt;0), the subject is determined as performing the inhaling motion (e.g., period of t1 to t2, t3 to t4 shown in the portion (A) of  FIG. 15 ). The time of transitioning from the exhaling motion to the inhaling motion (i.e., time at which dW/dt=0, or time at which dW/dt changes from a negative value to a positive value) is then specified (e.g., time t2, t4 shown in the portion (A) of  FIG. 15 ). 
     The bioelectrical impedance (e.g., bioelectrical impedance shown with an outlined circle in the portion (B) of  FIG. 15 ) acquired at the time closest to or the time same as the time of transitioning from the exhaling motion to the inhaling motion is extracted from the time-series data of the b bioelectrical impedance Z, and the average value of the extracted data is decided as a representative value of the bioelectrical impedance Z. The average value of the waist length acquired at the time closest to or the time same as the time of transitioning from the exhaling motion to the inhaling motion is decided as a representative value of the waist length W of the subject. 
     The method of deciding the representative value of the bioelectrical impedance described above merely shows one example. A case of using the bioelectrical impedance acquired at the timing of transitioning from the exhaling motion to the inhaling motion as the representative value has been shown, but the bioelectrical impedance acquired at the timing of transitioning from the inhaling motion to the exhaling motion may be used as the representative value. Instead of simply extracting specific data from the time-series data of the bioelectrical impedance Z and obtaining the average value thereof to decide the representative value, other calculations or the like may be added to decide the representative value. In either case, the representative value of the bioelectrical impedance Z merely needs to be decided in association with the breathing motion of the subject detected from the fluctuation of the waist length of the subject. 
     In the body fat measurement device  1 B according to the present embodiment, various types of fat mass are calculated using the representative value of the waist W and the representative values of the bioelectrical impedances Zt, Zs obtained in the above manner. Equations (1) to (4) shown in the first embodiment are used for the equations for calculating the same. 
       FIG. 16  is a flowchart showing the operation procedures of the body fat measurement device in measuring the visceral fat area, the subcutaneous fat area, and the body fat percentage using the body fat measurement device according to the present embodiment. In the figure, the same step numbers are denoted for the steps similar to the first embodiment, and the detailed description thereof will not be repeated herein. 
     With reference to  FIG. 16 , the control unit  10  accepts the input of the height H, the weight Wt and the like as physical information other than the waist length W (step S 21 ). The accepted subject information is temporarily saved in the memory  29 . 
     The control unit  10  then outputs a command to start the measurement of the waist length to the waist length measurement unit  30 , and the waist length measurement unit  30  starts the measurement of the waist length W based thereon (step S 1 A). 
     The control unit  10  determines whether or not an instruction to start the measurement is made (step S 2 ). The control unit  10  waits until the instruction to start the measurement is made (NO in step S 2 ). The control unit  10  proceeds to step S 3  if the instruction to start the measurement is detected (YES in step S 2 ). 
     The control unit  10  then sets the electrode (step S 3 ), and the constant current generation unit  21  flows a constant current between the upper limb and the lower limb based on the control of the control unit  10  (step S 4 ). In this state, the potential difference detection unit  23  detects the potential difference between the abdominal electrodes serving as the selected potential difference detection electrode over a plurality of times at a predetermined interval for a predetermined period defined in advance based on the control of the control unit  10  (step S 5 ). 
     The control unit  10  determines whether or not the detection of the potential difference is completed for the combinations of all abdominal electrode pairs serving as the potential difference detection electrode defined in advance (step S 6 ). The control unit  10  proceeds to the process of step S 3  if determined that the detection of the potential difference is not completed for the combination of all of the abdominal electrode pairs serving as the potential difference detection electrode defined in advance (NO in step S 6 ), and selects the non-selected abdominal electrode pair. The control unit  10  thereby detects, in order, the potential difference between the abdominal electrodes of the potential difference detection electrode pair of a plurality of pairs. 
     When the detection of the potential difference is completed for the combination of the abdominal electrode pairs serving as the potential difference detection electrode pair defined in advance (YES in step S 6 ), the impedance measuring portion  12  calculates the time-series data of the bioelectrical impedances Zt1 to Zt4 based on the current value of the constant current generated by the constant current generation unit  21  and flowed through the body and the time-series data of each potential difference detected by the potential difference detection unit  23  (step S 7 ). The time-series data of the bioelectrical impedances Zt1 to Zt4 calculated by the impedance measuring portion  12  is associated with the time-series data of the waist length W measured by the waist length measurement unit  30 , and temporarily saved in the memory  29 . 
     The control unit  10  then sets the electrodes again (step S 8 ), and the constant current generation unit  21  flows a constant current between the abdominal electrodes serving as the selected constant current application electrode based on the control of the control unit  10  (step S 9 ). In this state, the potential difference detection unit  23  detects the potential difference between the abdominal electrodes serving as the selected potential difference detection electrode over a plurality of times at a predetermined interval for a predetermined period defined in advance based on the control of the control unit  10  (step S 10 ). 
     The control unit  10  determines whether or not the application of the constant current and the detection of the potential difference are completed for all of the combinations of the constant current application electrode pairs and the potential difference detection electrode pairs defined in advance (step S 11 ). The control unit  10  proceeds to the process of step S 8  if determined that the application of the constant current and the detection of the potential difference are not completed for all of the combinations of the constant current application electrode pairs and the potential difference detection electrode pairs defined in advance (NO in step S 11 ), and selects the non-selected electrode pair. In this manner, the control unit  10  performs constant current application and potential difference detection, in order, on all of the combinations of the constant current application electrode pair and the potential difference detection electrode pair defined in advance. 
     When the application of the constant current and the detection of the potential difference are completed for all of the combinations of the constant current application electrode pairs and the potential difference detection electrode pairs defined in advance (YES in step S 11 ), the impedance measuring portion  12  calculates the time-series data of the bioelectrical impedances Zs1 to Zs4 based on the current value of the constant current generated by the constant current generation unit  21  and flowed through the body and the time-series data of each potential difference detected by the potential difference detection unit  23  (step S 12 ). The time-series data of the bioelectrical impedances Zs1 to Zs4 calculated by the impedance measuring portion  12  is associated with the time-series data of the waist length W measured by the waist length measurement unit  30 , and temporarily saved in the memory  29 . 
     The control unit  10  then outputs a command to end the measurement of the waist length to the waist length measurement unit  30 , and the waist length measurement unit  30  ends the measurement of the waist length W based thereon (step S 12 A). Thereafter, the body fat mass calculating portion  13  decides the representative values of the bioelectrical impedances Zt1 to Zt4 and the bioelectrical impedances Zs1 to Zs4 and decides the representative value of the waist length W based on the time-series data of the bioelectrical impedances Zt1 to Zt4 and the time-series data of the bioelectrical impedances Zs1 to Zs4, which are temporarily saved in the memory  29  and associated with the times-series data of the waist length W (step S 12 B). The method of deciding the representative value is as described above. 
     The visceral fat mass calculating part  16  then calculates the visceral fat area Sv based on the representative value of the actually measured waist length W, the representative value of the calculated bioelectrical impedances Zt1 to Zt4, and the representative value of the bioelectrical impedances Zs1 to Zs4 (step S 13 ). The visceral fat area Sv is calculated from equation (1). In the case where four sets of abdominal electrode groups, each set including four abdominal electrodes A 11 , A 12 , A 21 , A 22 , are arranged parallel to each other as mentioned above, the average value of the representative values of the four bioelectrical impedances Zt1 to Zt4 and the average value of the representative values of the four bioelectrical impedances Zs1 to Zs4, for example, are respectively substituted to equation (1). 
     The subcutaneous fat mass calculating part  17  then calculates the subcutaneous fat area Ss based on the representative value of the actually measured waist length W, and the representative value of the calculated bioelectrical impedances Zs1 to Zs4 (step S 14 ). The subcutaneous fat area Ss is calculated by substituting the waist length W and the calculated bioelectrical impedance Zs to equation (2). In the case where four sets of abdominal electrode groups, each set including four abdominal electrodes A 11 , A 12 , A 21 , A 22 , are arranged parallel to each other as mentioned above, the average value of the representative values of the four bioelectrical impedances Zs1 to Zs4, for example, is substituted to the bioelectrical impedance Zs in equation (2). 
     The total fat mass calculating part  14  calculates the fat free mass FFM based on the height H of the physical information accepted by the control unit  10  in step S 1  and the representative value of the calculated bioelectrical impedance Zt (step S 15 ). The fat free mass FFM is calculated by equation (3). In the case where four sets of abdominal electrode groups, each set including four abdominal electrodes A 11 , A 12 , A 21 , A 22 , are arranged parallel to each other as mentioned above, the average value of the representative values of the four bioelectrical impedances Zt1 to Zt4, for example, is substituted to the bioelectrical impedance Zt in equation (3). 
     The total fat mass calculating part  14  calculates the body fat percentage based on the weight Wt of the physical information accepted by the control unit  10  in step S 1 , and the fat free mass FFM calculated by the total fat mass calculating part  14  in step S 15  (step S 16 ). The body fat percentage is calculated from equation (4). 
     The display unit  26  displays each measurement result based on the control of the control unit  10  (step S 17 ). 
     The body fat measurement device  1 B then ends the body fat mass measurement process including the visceral fat area measurement process, the subcutaneous fat area measurement process, and the body fat percentage measurement process. 
     By adopting the configuration of the body fat measurement device  1 B according to the present embodiment described above, the waist length of the subject  300  can be automatically measured with a simple configuration of detecting the wrapping length of the belt  140  of the bioelectrical impedance measurement abdomen attachment unit  100 B at the time of measurement. Therefore, a body fat measurement device capable of performing the body fat measurement at high accuracy by calculating the body fat mass using the information of the actually measured waist length is obtained. 
     Furthermore, with the above-described configuration, the breathing state of the subject  300  can be detected at high accuracy with a simple configuration of detecting the fluctuation of the wrapping length of the belt  140  of the bioelectrical impedance measurement abdomen attachment unit  100 B at the time of measurement. Through the use of such a detection method, the change in waist length of the subject  300  involved in the breathing motion can be captured at high accuracy. Thus, the bioelectrical impedance can be accurately measured excluding the influence of the fluctuation of the bioelectrical impedance that occurs with the breathing motion by acquiring the value of the bioelectrical impedance as the time-series data using the above-described detection method, and associating the same with the breathing motion of the subject  300  to decide the representative value of the bioelectrical impedance. As a result, a body fat measurement device capable of measuring the body fat mass at high accuracy can be inexpensively manufactured. In particular, since the bioelectrical impedance needs to be measured with the electrode  113  arranged in contact with the abdomen  301  of the subject  300  in order to measure the visceral fat mass and the subcutaneous fat mass at the abdomen at high accuracy, the visceral fat mass and the subcutaneous fat mass at the abdomen can be calculated at high accuracy with the body fat measurement device  1 B of the above configuration. 
     In the first and second embodiments described above, the case where the band winding mechanism including a protrusion spring is used for the biasing portion has been described, but a rubber member, a constant load spring, and the like may be used in place of the spring. In particular, in the case where the constant load spring is used, the force of winding the band, that is, the force that acts in the direction of moving the electrode support and the attachment portion closer is maintained constant regardless of the pulled-out amount of the band, and thus the abdomen of the subject is constantly tightened with a constant tightening strength by the bioelectrical impedance measurement abdomen attachment unit, whereby the electrode can always be pressed against the abdomen of the subject with a constant load. 
     In the first and second embodiments of the present invention described above, the case where the belt with teeth is used for the belt has been described, but a belt without teeth may also be used as the belt. In such a case, a pulley without teeth is used for the pulley provided at the belt feeding portion, and a mechanism or the like for fixing the belt by friction is adopted for the fixing mechanism provided at the attachment portion. 
     In the second embodiment of the present invention described above, the case where the waist length measurement unit has a configuration of detecting not only the waist length of the subject but also the fluctuation amount thereof has been described, but a configuration of obtaining even the fluctuation amount of the waist length is not always necessary, and may not be carried out in order to simplify the device. 
     In the first and second embodiments of the present invention, the case where the electrode is arranged in contact with the front surface of the abdomen of the subject has been described, but the present invention is also applicable to a body fat measurement device configured to arrange the electrodes so as to be brought into contact with the back surface of the abdomen or the side (flank) of the subject, and a bioelectrical impedance measurement abdomen attachment unit arranged therein. 
     In the first and second embodiments of the present invention, a body fat measurement device in which the electrode is intended to be arranged in contact with the four limbs of the subject using the impedance measurement upper limb attachment unit and the lower limb attachment unit has been described, but the application of the present invention is not limited to such a body fat measurement device, and may be applied to a body fat measurement device in which the electrode is not arranged in contact with the four limbs and the electrode is intended to be arranged in contact with only the body (abdomen). 
     Furthermore, in the first and second embodiments of the present invention, the case where the present invention is applied to a body fat measurement device in which the subject is intended to take the laid position at the time of measurement and a bioelectrical impedance measurement abdomen attachment unit arranged therein has been described, but the present invention is also applicable to a body fat measurement device in which the subject is intended to take the posture other than the laid position such as a face-down position, a side position, a standing position and a sitting position, and a bioelectrical impedance measurement abdomen attachment unit arranged therein. 
     The embodiments disclosed herein are illustrative in all aspects and should not be construed as being restrictive. The scope of the invention is defined by the claims, and all modifications equivalent in meaning to the claims and within the scope thereof are intended to be encompassed therein.