Abstract:
The body fat percentage for a person is estimated from the BMI of the person by employing a multiple regression analysis using the reciprocal of the BMI (1/BMI) as the independent variable. In other embodiments, potentially independent and easily obtained variables such as age, sex, and ethnicity are also used in conjunction to provide precise estimates of the body fat percentage. Devices for estimating the body fat percentage can be implemented as calculators, smart scales, and Internet web sites.

Description:
RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/136,378 entitled METHOD AND APPARATUS FROM DETERMINING BODY FAT PERCENTAGE FROM A BODY MASS INDEX, filed on May 27,1999, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to artificial intelligence and more particularly to a method and apparatus for estimating body fat percentage of a person 
     BACKGROUND OF THE INVENTION 
     With the steady increase in worldwide rates of obesity, the National Institutes of Health (NIH) and the World Health Organization (WHO) have recently adopted similar body weight standards for diagnosing overweightness and obesity. For example, a person is considered overweight according to these standards if the person&#39;s body weight adjusted for height, referred to a body weight index (BMI=weight/height 2 ), is greater than 25 kg/m 2  and obese if the BMI is greater than 30 kg/m 2 . Conversely, being underweight is defined as having a BMI less than 18.5 kg/m 2 . Practitioners have been using these body weight guidelines in diagnosing the presence of excessive adiposity and prescribing treatment for their overweight patients. 
     Lately, there has been increasing interest in quantifying a person&#39;s total body fat or the person&#39;s body fat percentage rather than BMI as a direct measure of obesity. The main assumption of the BMI standards is that body mass, adjusted for stature, is associated with body fatness and consequent morbidity and mortality. However, there some individuals who are overweight according to the BMI standards, but not overfat (e.g. body builders), Similarly, there are some lean individuals such as marathon runners who are not “underweight” in accordance with the BMI standards but who have a very low body fat content Due to the variations among the population, there is at present no accepted consensus on how BMI and body fat are linked. 
     Accordingly, several approaches have been developed for measuring body fat, but all of these approaches require special equipment. For example, am underwater or hydrostatic weighing technique compares a person&#39;s weight in air and the person&#39;s weight in water and, taking the person&#39;s lung volume into account, computes the person&#39;s body volume and density The body fat percentage is then estimated from the calculated body density. This technique, however, requires special equipment for weighing a person .underwater such as stainless steel water tanks. 
     Another body fat measurement technique is known as “dual energy X-ray absorptiometry” (DXA), in which a person is irradiated with X-rays to measure the bone mineral content and body fat percentage by differences in the X-ray absorption rates. This technique, too, requires special equipment to produce and measure the X-rays. Still another technique includes drinking heavy water comprising D 2 O or  3 H 2 O and calculating the deuterium or tritium dilution to determine the total body water, from which the body fat percentage can be estimated. This approach require special ingredients, equipment, and expertise. 
     Bioelectronic impedance analysis (BIA) can also be used to estimate body fat percentage from measuring the electrical impedance of a person and correlating the impedance with the person&#39;s standing height and body weight In contrast with the previous techniques, the BIA can be performed with relatively inexpensive pieces of equipment. 
     In all of these techniques, however, some additional equipment is required, ranging from the X-ray machines to bioelectronic impedance measurement devices. here is a need for a method and apparatus for estimating the body fat percentage, which is simple to apply and does not require special equipment or expertise. In fact, there is a need for a technique that can be performed over the Internet without requiring the user to purchase special equipment. 
     SUMMARY OF THE INVENTION 
     These and other needs are addressed by the present invention in which the body fat percentage for a person is estimated from the BMI of the person. The present invention stems from the discovery that the models for body fat percentage can be developed using a multiple regression analysis with the reciprocal of the BMI (1/BMI) as the independent variable. Use of the 1/BMI terms advantageously linearizes the data and avoids the need for logarithmic conversion or inclusion of power terms and therefore simplifies the computing apparatus and programs. Preferably, other potentially independent and easily obtained variables such as age, sex, and ethnicity are also used to provide precise estimates of the body fat percentage. All of such variables can readily be determined without the use of special equipment or expertise. 
     One aspect of the invention relates to an apparatus, a machine-implemented method, and software for estimating a body fat percentage of a person put indicating data concerning the person is received, and the body fat percentage of the person is then estimated based on a reciprocal of a body mass index (BMI), which is the quotient of the weight of the person divided by the square of the height of the person. Then the estimated body fat percentage is output to the user, Various embodiments of the apparatus include a body fat calculator, a personal computer programmed to estimate body fat percentage, a web server that provides a web site for estimating body fat percentages, and a scale that is equipped to weigh a person and use the measured weight to estimate the body fat percentage. 
     Still other objects and advantages of the present invention will become readily apparent from the following detailed description, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
     FIG. 1 depicts a body fat calculator in accordance with one embodiment of the present invention. 
     FIG. 2 depicts an electrical block diagram of the body At calculator depicted in FIG.  1 . 
     FIG. 3 is a flowchart illustrating the operation using the body fat calculator depicted in FIG.  1 . 
     FIGS.  4 ( a ),  4 ( b ),  4 ( c ),  4 ( d ),  4 ( e ),  4 ( f ), and  4 ( g ) depict screens displayed by the body fat calculator depicted in FIG.  1 . 
     FIG. 5 depicts a scale in accordance with one embodiment of the present invention. 
     FIG. 6 depicts an electrical block diagram of the scale depicted in FIG.  5 . 
     FIG. 7 is a flowchart illustrating the operation using the scale depicted in FIG.  5 . 
     FIG. 8 depicts a screen displayed in one mode by the scale depicted in FIG.  5 . 
     FIGS.  9 ( a ),  9 ( b ),  9 ( c ),  9 ( d ),  9 ( e ),  9 ( f ), and  9 ( g ) depict screens displayed in another mode by the scale depicted in FIG.  5 . 
     FIG. 10 is a diagram of a computer network that can be used to implement one embodiment of the present invention. 
     FIG. 11 is a flowchart illustrating the operation using the computer network depicted in FIG.  10 . 
     FIG. 12 is a diagram that depicts a computer system that can be used to implement one embodiment of the present invention. 
     FIG. 13 is a graph of BMI plotted against body fat percentage, 
     FIG. 14 is a graph of the reciprocal of BMI plotted against body fat percentage. 
     FIG. 15 is a graph of 1/BMI and sex plotted against body fat percentage. 
     FIG. 16 is a graph of 1/BMI, age, and sex plotted against body fat percentage. 
     FIG. 17 is a graph of 1/BMI and age plotted against body fat percentage. 
     FIG. 18 is a graph of 1/BMI, age, sex, and ethnicity plotted against body fat percentage. 
     FIG. 19 is a graph of body fat percentage measured by DXA plotted against body fat percentage as determined by the 4-Compartment approach for males. 
     FIG. 20 is a graph of body fat percentage measured by DXA plotted against body fat percentage as determined by the 4-Compartment approach for females. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Methods and apparatuses for estimating body fat percentage are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention. 
     CONCEPTUAL OVERVIEW 
     In accordance with one aspect of the present invention, a study was conducted to develop formulas for expressing body fat percentage in terms of BMI and other potential independent variables such as age and ethnicity. Although the present application describes formulas that were developed from a particular battery of experiments by way of example, it is to be understood that the present invention is not so limited and may be used with results from other experimental configurations. 
     Accordingly, three groups of experimental subjects were recruited in New York City, USA, Cambridge, UK, and Jekei, Japan. The body fat of the subjects was measured by DXA at all three centers, and, in addition, tritium dilution volume and body density were quantified in the USA and UK sites to the body fat percentage by the 4-Compartment method. Subjects were a convenience sample recruited through advertisements in local newspapers, posted flyers, or through referral for body weight evaluation. The subject pool consisted of 1626 healthy adults, ranging in age, body weight, and ethnicity. In this experiment, three ethnic groups were evaluated: African American at the USA cite, Caucasian at the USA and UK sites, and Asian at the Japan site. 
     Once passing the screening evaluation, the BMI for the subjects was calculated, and the subjects completed all the available the direct body fat measurements on the same day. FIG. 13 is a graph of the subjects&#39; BMI plotted against the measured body fat percentages of the subjects. Females are marked in the graph with a solid circle and males are indicated by a square. By inspecting the graph, there is a relationship between the body fat percentage and BMI, with the body fat percentage being distributed over a curve for both the males and females. 
     Next, the reciprocal of the BMI (1/BMI) was plotted against the body fat percentage, which resulted in the graph shown in FIG. 14. A linear relationship between 1/BMI and the body fat percentage was derived by a regression model, which finds a line that minimizes the square of the errors. Therefore, the body fat percentage can be estimated from the reciprocal of the BMI according to the following equation: 
     
       
         Body Fat %= A−K ×1/BMI,  (1) 
       
     
     where A and K are constants, and BMI is the body mass index. The precise values of the A and K derive from the experiment results and will differ, depending on the experiments that were performed. In this model, the correlation coefficient is 0.576. 
     It was observed that, in general, females have a higher body fat percentage than corresponding males. Thus, the correlation in the model of equation (1) can be improved by taking the sex of the subjects into account, using the following equation, for example: 
     
       
         Body Fat %=− K ×1/BMI− B ×sex+ C ×sex×1/BMI,  (2) 
       
     
     where A, B, C, and K are constants, “sex” is a variable that indicates the sex of the person (e.g. 0 for females and 1 for males), and BMI is the body mass index of the person. The precise values of A, B, C, and K derive from the experiment results and will differ from implementation to implementation, depending on the experiments that were performed. In this model, a graph of which is illustrated in FIG. 15, the correlation coefficient raises to 0.885. 
     Furthermore, it was found that older subjects tend to have a higher body fat percentage than their younger counterparts. Thus, the correlation can be improved by taking the age of the subjects into account, using the following equation, for example: 
     
       
         Body Fat %= A−K ×1/BMI− B ×age− C ×sex+ D ×sex×age+ E ×sex×1/BMI,  (3) 
       
     
     where A, B, C, D, E, and K are constants, “sex” is a variable that indicates the sex of the person (e.g. 0 for females and 1 for males), “age” is a variable that indicates the age of the person, and BMI is the body mass index of the person. The precise values of A, B, C, D, E, and K derive from the experiment results and will differ from implementation to implementation, depending on the experiments that were performed In this model, a graph of which is illustrated in FIG. 16, the correlation coefficient raises to 0.889. 
     If only the age but not the sex of the person was considered, this scenario can be modeled with the following equation: 
     
       
         Body Fat %= A−K ×1/BMI− B ×age,  (4) 
       
     
     where A, B, and K are constants, “age” is a variable that indicates the age of the person, and BMI is the body mass index of the person. The precise values of A, B, and K derive from the experiment results and will differ, depending on the experiments that were performed. In this model, a graph of which is illustrated in FIG. 17, the correlation coefficient is 0.576. 
     Since the sex of the person has a stronger influence on the body fat percentage, it is possible to take sex into account into the age model of equation (4) with two sex-specific regression formulas, one for males and the other for females, rather than employing sex as a variable. In this case, the following equations may be used, in which the corresponding constants A 1  vs. A 2  and B 1  vs. B 2  are different: 
     
       
         Body Fat % (male)= A   1 − K   1 ×1/BMI− B   1 ×age,  (5) 
       
     
     
       
         Body Fat % (female)= A   2 − K   2 ×1/BMI− B   2 ×age,  (6) 
       
     
     Further improvements in the correlation can be attained by taking the ethnicity of the subjects into account For example, it has been found that Asian tended to have a higher body fat percentage for a given BMI than did African Americans or Caucasians, particularly at the lower age ranges. Thus, the correlation can be improved by taking the ethnicity of the subjects into account, using the following equation, for example: 
     
       
         Body Fat %= A−K ×1/BMI−B×sex− C ×age+ D ×asian×1/BMI+ E ×asian×age+ F ×sex×age+ G ×sex×1/BMI,  (7) 
       
     
     where A, B, C, D, E, F, G. and K are constants, “sex” is a variable that indicates the sex of the person (e.g. 0 for females and 1 for males), “age” is a variable that indicates the age of the person, “asian” is a variable that indicates whether the person is belongs to an Asian ethnic group, and BMI is the body mass index of the person. The precise values of A, B, C, D, E, F, G, and K derive from the experiment results and will differ from implementation to implementation, depending on the experiments that were performed. In this model, a graph of which is illustrated in FIG. 18, the correlation coefficient raises to 0.896. 
     In the experiment, two measurements of body fat were performed at the USA and UK sites, one based on DXA and the other using a 4-Compartment technique, which uses the measured mineral mass, total body water (which requires drinking heavy water), and body density/volume values for a person These measurements were also regressed in males and females (see FIGS. 19 and 20, respectively) to develop the following equation: 
     
       
         4- C  Body Fat % (4- C )= A−K ×DXA Body Fat %,  (8) 
       
     
     where A and K am constants and “DXA Body Fat %” is the body fat percentage based on the DXA technique is the body mass index of the person. The correlation constant for males in this experiment is 0.9364 and 0.934 for females, showing a high correlation for between the DXA technique and the 4-C approach. The 4-C body fat percentage can be reliably estimated from the DXA body fat percentage, without having the subject drink heavy water. 
     BODY FAT CALCULATOR 
     One aspect of the present invention relates to a simple device for estimating the body fat percentage for a person FIG. 1 depicts a body fat calculator  1  in accordance with one embodiment of the present invention, which does not require the use of special or expensive equipment, such as X-ray machines, or exotic chemicals, such as heavy water. 
     Various components are disposed on the front face of the body fat calculator  1 , including a power switch  2 , an up key  3 , a down key  4 , an enter key  5 , and a display screen  6 . The power switch  2  is provided for turning the body fat calculator  1  on and off. The up key  3  and the down key  4  permit a user to enter data about the user by incrementing or decrementing a display value corresponding to the user&#39;s standing height body weight, sex, age, and ethnicity. The display screen  6  can be a liquid crystal display (LCD), or LED display, etc., for displaying numbers and icons to the user in the course of operation. 
     FIG. 2 is an electrical block diadem of one implementation of the body fat calculator  1 . This implementation of the body fat calculator  1  includes a microcontroller (or CPU)  7  that is coupled to the input elements of the body fat calculator  1 , including the up key  3 , the down key  4 , and the enter key  5 . The power switch  2  is coupled to the microcontroller  7  and to a power supply  8 , which can be a battery disposed within the body fat calculator  1 , for switching power on and off to the microcontroller  7 . The display screen  6  is also coupled to the microcontroller  7  through a display driver (not shown). 
     FIG. 3 is a flowchart, illustrating the operation of using the body fat calculator  1  in accordance with one embodiment of the present invention. When a user begins to use the body fat calculator  1 , the user presses the power switch  2 , which connects the power source  8  to the microcontroller  7 . Upon application of power, the microcontroller  7  undergoes an initialization sequence (step  1 ), which sets up the display screen  6  to display an initial display screen. By way of example, one initial display screen is shown in FIG.  4 ( a ), but it is to be understood that the present invention is not so limited and various screens may be shown. 
     In the illustrated embodiment, by way of example, the initial display screen  400  includes areas for indicating the sex, age, height, weight, and ethnicity of the user. In other embodiments, additional and/or fewer areas for corresponding variables may be employed. In the initial display screen, default values for the age (25 years), height (170 cm), weight (55 kg) are displayed, and all supported values of sex (male or female) and ethnicity (Asian, black, white) arc shown. Areas are also reserved for outputting the BMI, body fat percentage, and body fat mass, but these values are displayed later after being calculated. 
     At step  2 , the user presses the up key  3  to indicate that he is a male or the down key  4  to indicate that she is a female. In response, only the corresponding icon is displayed (with the other icon being turned off). For example, if the user pressed the down key  4  to indicate that she is female, then the female icon is displayed and the male icon is turned off, as illustrated in screen  402  of FIG.  4 ( b ). Upon reaching the desired value for sex, the user presses the enter key  5 , which is tested at step  3 , and execution proceeds to step  4 . 
     At step  4 , the user repeatedly presses the up key  3  or the down key  4  to add one or subtract one, respectively, from the displayed age, until the desired age is reached. In the example, illustrated as screen  404  in FIG.  4 ( c ), the age has been incremented to 27 years. Upon reaching the desired age, the user presses the enter key  5 , which is tested at step  5 , and execution proceeds to step  6 . 
     At step  6 , the user repeatedly presses the up key  3  or the down key  4  to add a predetermined amount (such as 5 cm) or subtract the predetermined amount, respectively, from the displayed height, until the desired height is reached. In the example, illustrated as screen  406  in FIG.  4 ( d ), the height has been decremented to 165 cm. Upon reaching the desired height, the user presses the enter key  5 , which is tested at step  7 , and execution proceeds to step  8 . Although metric units are depicted in this example, U.S. customary units such as inches may also be employed. 
     At step  8 , the user repeatedly presses the up key  3  or the down key  4  to add a predetermined amount (such as 1 kg) or subtract the predetermined amount, respectively, from the displayed weight, until the desired height is reached. In the example, illustrated as screen  408  in FIG.  4 ( e ), the weight has been changed to 53 kg Upon reaching the desired weight, the user presses the enter key  5 , which is tested at step  9 , and execution proceeds to step  10 . Although metric units are depicted in this example, U.S. customary units such as pounds may also be employed. 
     At step  10 , the user repeatedly presses the up key  3  or the down key  4  to select one of the supported ethnicitics. In the example, illustrated as screen  410  in FIG.  4 ( f ), the user has selected the Asian ethnicity and presses the enter key  5 , which is tested at step  11  for continuation to step  12 . 
     At step  12 , the information that was received from the user is used to calculate the BMI, body fat percentage, and body fat mass. In this implementation the BMI is calculated as the weight/height 2 , and the body fat percentage is calculated using equation (7) explained herein above. The body fat miss is calculated as the product of the body fat percentage and the weight This information is displayed on the display screen  6 , as illustrated in the output display screen  412  of FIG.  4 ( g ). After a preset period of time, for example 30 seconds, as determined by an internal timer of microcontroller  7 , the body fat controller  1  automatically shuts itself off to conserve power. 
     BODY FAT CALCULATOR SCALE 
     One embodiment of the present invention is a scale that can estimate the body fat percentage of a person. Referring to FIG. 5, a scale  11  comprises an under body  12  and an upper body  13 . Disposed on the top face  13 A of the upper body  13  include a power switch  14 , a mode key  15 , an up key  16 , a down key  17 , an enter key  18 , and a display screen  19 . The power switch  15  is provided to turn the scale  11  on and off. The mode key  15 , the up key  16  and the down key  17  permit a user to enter data about the user such as the user&#39;s standing height, sex, age, and ethnicity. The display screen  19  can be a liquid crystal display (LCD), or LED display, etc., for displaying numbers and icons to the user in the course of operation. 
     FIG. 6 is an electrical block diagram of one implementation of the scale  11 . This implementation of the scale  11  includes a microcontroller (or CPU)  20  that is coupled to the input elements of the scale  11 , including mode key  15 , the up key  16  and the down key  17 . The power switch  14  is coupled to the microcontroller  20  and to a power supply  22 , which can be a battery disposed within the scale  11 , for switching power on and off to the microcontroller  20 . The display screen  19  is also coupled to the microcontroller  20  through a display driver (not shown). Furthermore, the microcontroller  20  is coupled to an electronic weight scale  21 , which is configured for providing weight information to the microcontroller  20  when a person is standing on the upper body  12 . 
     FIG. 7 is a flowchart, illustrating the operation of using the scale  11  in accordance with one embodiment of the present invention. When a user begins to use the scale  1   1 , the user presses the power switch  14 , which connects the power source  22  to the microcontroller  20 . Upon application of power, the microcontroller  20  undergoes an initialization sequence (step  20 ), which initialization the scale  11 . 
     At step  21 , the microcontroller  20  check to determined if the user has presses the fat mode button  15 . If the user has not pushed the fat mode button  15 , the scale  11  then measures the person&#39;s weight using the weight scale  21  (step  22 ) and displays the result in a display screen shown in FIG. 8 (step  23 ), in which, for example, the user weights 60 kg (about 132 lbs). After 30 seconds, tested in step  24 , the microcontroller  20  shuts the scale  11  off to converse power. 
     If, on the other hand, the fat mode button  15 , was pressed, then the microcontroller  20  sets up the display screen  19  to display an initial fat display screen  900 . By way of example, one initial display screen  900  is shown in FIG.  9 ( a ), but it is to be understood that the present invention is not so limited and various screens may be shown. 
     In the illustrated embodiment, by way of example, the initial fat display screen  900  includes areas for indicating the sex, age, height, weight, and ethnicity of the user. In other embodiments, additional and/or fewer areas for corresponding variables may be employed. In the initial display screen, default values for the age (25 years), height (170 cm), weight (55 kg) are displayed, and all supported values of sex (male or female) and ethnicity (Asian, black, white) are shown. Areas are also reserved for outputting the BMI, body fat percentage, and body fat mass, but these values are displayed later after being calculated. 
     At step  25 , the user presses the up key  16  to indicate that he is a male or the down key  17  to indicate that she is a female. In response, only the corresponding icon is displayed (with the other icon being turned off). For example, if the user pressed the down key  17  to indicate flat she is female, then the female icon is displayed and the male icon is turned off, as illustrated in screen  902  of FIG.  9 ( b ). Upon reaching the desired value for sex, the user presses the enter key  18 , which is tested at step  26 , and execution proceeds to step  27 . 
     At step  27 , the user repeatedly presses the up key  16  or the down key  17  to add one or subtract one, respectively, from the displayed age, until the desired age is reached. In the example, illustrated as screen  904  in FIG.  9 ( c ), the age has been incremented to 27 years. Upon reaching the desired age, the user presses the enter key  18 , which is tested at step  28 , and execution proceeds to step  29 . 
     At step  29 , the user repeatedly presses the up key  16  or the down key  17  to add a predetermined amount (such as 5 cm) or subtract the predetermined amount, respectively, from the displayed height, until the desired height is reached. In the example, illustrated as screen  906  in FIG.  9 ( d ), the height has been decremented to 165 cm. Upon reaching the desired height, the user presses the enter key  18 , which is tested at step  30 , and execution proceeds to step  31 . Although metric units are depicted in this example, U.S. customary units such as inches may also be employed. 
     At step  31 , the user repeatedly presses the up key  16  or the down key  17  to select one of the supported ethnicities. In the example, illustrated as screen  908  in FIG.  9 ( e ), the user has selected the Asian ethnicity and presses the enter key  18 , which is tested at step  32  for continuation to step  33 . At step  33 , the scale  11  then measures the person&#39;s weight using the weight scale  21 . The result is then displayed (step  34 ) in screen  91  shown in FIG.  9 ( f ), in which the user weights 53 kg. Although metric units are depicted in this example, U.S. customary units such as pounds may also be employed. 
     At step  34 , the information that was received from the user is used to calculate the BMI, body fat percentage, and body fat mass. In this implementation, the BMI is calculated as the weight/height 2 , and the body fat percentage is calculated using equation (7) explained herein above. The body fat mss is calculated as the product of the body fat percentage and the weight This information is displayed on the display screen  6 , as illustrated in the output display screen  912  of FIG.  49 ( g ). After a preset period of time, for example 30 seconds, as determined by an internal timer of microcontroller  20  in step  24 , the scale  11  automatically shuts itself off to conserve power. 
     BODY FAT ESTIMATION OVER A NETWORK 
     Another embodiment of the present invention related to performing body fat estimation over a network, such as a local area network (LAN), a wide-area network (WAN), or the Internet. FIG. 10 depicts a computer network in which a personal computers  20  is coupled, via a hub  31 , to a server  32  In this arrangement, a user at personal computer  30  desires to obtain the user&#39;s body fat percentage based on simple variables by interacting with server  32  over a computer network. 
     FIG. 11 illustrates the operation of this embodiment, in which the user obtains access to personal computer  30  (for example by login and password procedures) and then to server  32 , for example, by accessing a web site maintained at server  32  (step  1102 ). When the server  32  received a request for the web site, typical via a hypertext transfer protocol (HTTP) GET command with a URL designating the address of the web site. The server  32  receives the request (step  1104 ), fetches web page or other generates an input display image (step  1106 ) and transmits the web page to the personal computer  30 . 
     In response, the person computer receives and displays the web page (step  1108 ), which typically includes a form for inputting data. At step  1110 , the user enters the requested data, such as sex, age, height, weight, and ethnicity (or even BMI directly), and transfers the entered information to the server  32 , for example, by an HTTP POST command. In response, the server  32  receives the information, and makes the appropriate calculations to determine, inter alia, the body fat percentage based on at least some of the input variables, for example, by applying the above-explained regression equations (step  1112 ). The calculation results are then assembled into an output web page (step  1141  and transmitted to the user&#39;s personal computer  30  and displayed (step  1116 ). 
     HARDWARE OVERVIEW 
     FIG. 12 is a block diagram that illustrates a computer system  1200 , such as personal computer  30 , upon which an embodiment of the invention may be implemented. Computer system  1200  includes a bus  1202  or other communication mechanism for communicating information, and a processor  1204  coupled with bus  1202  for processing information. Computer system  1200  also includes a main memory  1206 , such as a random access memory (RAM) or other dynamic storage device, coupled to bus  1202  for storing information and instructions to be executed by processor  1204 . Main memory  1206  also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor  1204 . Computer system  1200  further includes a read only memory (ROM)  1208  or other static storage device coupled to bus  1202  for storing static information and instructions for processor  1204 . A storage device  1210 , such as a magnetic disk or optical disk, is provided and coupled to bus  1202  for storing information and instructions. 
     Computer system  1200  may be coupled via bus  1202  to a display  1212 , such as a cathode ray tube (CTR), for displaying information to a computer user. An input device  1214 , including alphanumeric and other keys, is coupled to bus  1202  for communicating information and command selections to processor  1204 . Another type of user input device is cursor control  1216 , such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor  1204  and for controlling cursor movement on display  1212 . This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. 
     The invention is related to the use of computer system  1200  for estimating body fat percentage. According to one embodiment of the invention, estimating body fat percentage is provided by computer system  1200  in response to processor  1204  executing one or more sequences of one or more instructions contained in main memory  1206 . Such instructions may be read into main memory  1206  from another computer-readable medium, such as storage device  1210 . Execution of the sequences of instructions contained in main memory  1206  causes processor  1204  to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory  1206 . In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the invention. Thus, embodiments of the invention are not limited to any specific combination of hardware circuitry and software. 
     The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to processor  1204  for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device  1210 . Volatile media include dynamic memory, such as main memory  1206 . Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus  1202  Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read. 
     Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor  1204  for execution For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system  1200  can receive the data on the telephone line and use an e d transmitter to convert the data to an infrared signal. An infrared detector coupled to bus  1202  can receive the data carried in the infrared signal and place the data on bus  1202 . Bus  1202  carries the data to main memory  1206 , from which processor  1204  retrieves and executes the instructions. The instructions received by main memory  1206  may optionally be stored on storage device  1210  either before or after execution by processor  1204 . 
     Computer system  1200  also includes a communication interface  1218  coupled to bus  1202 . Communication interface  1218  provides a two-way data communication coupling to a network link  1220  that is connected to a local network  1222 . For example, communication interface  1218  may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, communication interface  1218  may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented In any such implementation, communication interface  1218  sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information. 
     Network link  1220  typically provides data communication through one or more networks to other data devices. For example, network link  1220  may provide a connection through local network  1222  to a host computer  1224  or to data equipment operated by an Internet Service Provider (ISP)  1226 . ISP  1226  in turn provides data communication services through the worldwide packet data communication network, now commonly refereed to as the “Internet”  1228 . Local network  1222  and Internet  1228  both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network link  1220  and through communication interface  1218 , which carry the digital data to and from computer system  1200 , are exemplary forms of carrier waves transporting the information. 
     Computer system  1200  can send messages and receive data, including program code, through the network(s), network link  1220 , and communication interface  1218 . In the Internet examples a server  130  might transmit a requested code for an application program through Internet  1228 , ISP  1226 , local network  1222  and communication interface  1218 . In accordance with the invention, one such downloaded application provides for estimating body fat percentage as described herein. The received code may be executed by processor  1204  as it is received, and/or stored in storage device  1210 , or other non-volatile storage for later execution. In this manner, computer system  1200  may obtain application code in the form of a carrier wave. 
     While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended clams.