502

Asia Pac J Clin Nutr 2006;15 (4):502-507

Original Article

Is the BMI cut-off level for Japanese females for obesity
set too high? – A consideration from a body composition
perspective
Masaharu Kagawa PhD1, Kazuhiro Uenishi RD PhD2, Chiharu Kuroiwa RPT MSc3,
Miki Mori RD BSc2 and Colin W Binns MBBS MPH PhD1
12
3

School of Public Health, Curtin University of Technology, Perth, Australia
Kagawa Nutrition University, Saitama, Japan
Department of Physical Therapy, Koriyama Institute of Health Science, Fukushima, JapanThe aim of the study was to determine the sensitivity and specificity of the BMI cut-off points that have been
applied in the National Nutritional Survey in Japan (NNS-J) for young Japanese females. The relationshipbetween the body mass index (BMI) and percentage body fat (%BF) of 139 young Japanese females (aged 18-27
years old) was examined using dual energy x-ray absorptiometry (DXA) and anthropometry. The sensitivity andspecificity of the BMI cut-off point that has been in use in Japan was compared with the cut-off point proposed for
Asia-Pacific population (the WPRO classification). The regression equation calculated for the relationshipbetween the BMI and %BF using the DXA scan data was %BF = -15.152+2.058*BMI; R2 = 0.612, SEE = 3.66.
From this equation the BMI value that corresponded with %BF of 30% was calculated to be 21.9kg/m2 (95%CI:
16.9-28.6). From the sensitivity and specificity analysis, it was found that more than 90% of Japanese femaleswith %BF >30% were misclassified as “not obese” when the BMI value of 25kg/m2 was used to identify obese
individuals. The misclassification reduced to 60% when the BMI value of 23kg/m2 was used as a cut-off point.
The results indicate that the current classification used in the NNS-J may not precisely reflect the obesity status ofyoung Japanese females and a considerable proportion of females with a large fat deposition would be
misclassified as not obese. The current study shows the importance of including detailed body compositionassessments to determine obesity level of individuals.

Key Words: Body Mass Index, body fat, BMI cut-off points, Japanese, females

Introduction
Obesity is a well known risk factor of a number of healthproblems including hypertension, diabetes, high blood
glucose and cholesterol levels and cardiovascular diseases.
The World Health Organization (WHO) has proposedusing body mass index (BMI: body mass (kg)/stature(m)2)
as a simple screening tool of obesity with the value of
25kg/m2 as a cut-off point of “pre-obese”.1 While its
application to individuals may be problematic2,3 BMI has
been shown to have a high correlation with these obesityrelated health problems in epidemiological studies.4,5 Previous studies have suggested that Asians have a higher
percent body fat (%BF) than Caucasians at the same BMI
value and they are likely to develop health problems at
lower BMI values than Caucasians.6-11 This may be associated with ethnic differences in body proportion (i.e proportion of limb or trunk lengths in relation to stature).12
Considering ethnic differences in the BMI and risk ofdeveloping obesity-related health problems, the Regional
Office for the Western Pacific Region of WHO, together
with the International Association for the Study of Obesity(IASO) and the International Obesity Task Force (IOTF)
proposed BMI cut-off points that are suitable for populations living in the Asia-Pacific region (the WPRO

classification).13 In 2004, WHO proposed additional BMI
cut-off points of 23kg/m2, 27.5kg/m2, 32.5kg/m2 and37.5kg/m2 as levels to provide appropriate health advice,depend on ethnic background of the target population.14
The National Nutrition Survey in Japan (NNS-J) has
shown that obesity has been more prevalent among males
than females. Only 7% of the females aged 20-29 years
old in the 2002 survey were classified as “obese”.15 The
NNS-J classified obesity using the BMI classification
defined by the Japan Society for the Study of Obesity(JASSO),16 which used the same BMI cut-off points for“underweight” as the WHO classification (ie, 18.5kg/m2)
but classified individuals with the BMI value of 25kg/m2 as“obese” instead of “pre-obese”.

Correspondence address: Professor Colin Binns
School of Public Health, Curtin University of Technology GPO
Box U1987 Perth WA 6845
Tel: +61-8-9266-2952; Fax: +61-8-9266-2958
E-mail: c.binns@curtin.edu.au
Accepted 30th April 2006

M Kagawa, K Uenishi, C Kuroiwa, M Mori and CW Binns

Table 1. Physical characteristics of Japanese females
obtained from anthropometry and whole-body DXA scan
Japanese females (N = 139)
mean ± standard deviation
Age (years)

20.4 ± 1.3

Stature (cm)158.8 ± 5.0

Body mass (kg)52.5 ± 6.1

BMI (kg/m2)

20.8 ± 2.2

Percent body fat
using DXA (%)

27.6 ± 5.9

BMD (g/cm2)

1.14 ± 0.07

BMC (g)2351.6 ± 266.5

Sum of skinfolds (mm)124.5 ± 35.5

Height-corrected sum ofskinfolds (mm)133.5 ± 38.3

Individuals who had their BMI ≥25kg/m2 are advised toundergo further assessment on their waist circumference
in order to examine abdominal fat distribution. However,the JASSO classification was not proposed with consideration of the actual relationship between BMI and bodyfat deposition (BMI-%BF relationship) of Japanese population. As the BMI itself does not reflect the actual
amount of body fat of individuals and also because ofethnic differences in the BMI-%BF relationship, it ispossible that the JASSO classification may underestimate
the proportion of Japanese females with a considerable
amount of body fat. Several Japanese studies have described obese individuals who were misclassified as“normal” using the WHO or the JASSO classifications as“masked obese”.17-19 It is possible that misclassifications
reported in previous studies are because of the applicationof inappropriate BMI cut-off points that do not reflect
their actual body fatness.

503

The aim of the current study was to determine sensitivity
and specificity of the JASSO classification in young Japanese females by assessing the BMI-%BF relationship of
the group based on the body composition results obtained
from whole-body dual energy x-ray absorptiometry(DXA) and anthropometry.
MethodThe study was approved by the Human Research Ethics
Committees of Curtin University of Technology and Kagawa Nutrition University. The study adhered to the principles of medical research established by the National
Health and Medical Research Council.20 In the current
study 139 healthy Japanese females volunteers aged 1827years old were recruited. Each subject was provided
with a written informed consent form in which the purpose of the study and the radiation exposure involved in
the study were explained. The confidentiality of the results was guaranteed. Participants were asked if they
were pregnant prior to undergo body composition assessment.
Dual energy x-ray absorptiometry (DXA)
Body composition of subjects was assessed using dual
energy x-ray absorptiometry (DXA; Lunar® DPX-LIQ).
This method is based on multi-compartment model andconsidered as one of the methods that provide relatively
valid estimation of %BF.21-23 A whole-body DXA scan
provides information on bone mineral density (BMD),
bone mineral content (BMC), fat mass, lean mass, and%BF of the entire body and different body sections (eg.,head, trunk and limbs). Every subject was asked to remove all accessories and metallic items before their bodycomposition measurements. The DXA measurements
were completed in approximately 10 min and all measurements were conducted by an accredited technician.

50
45
40
35

%BF

30

Japanese females

25%BF = -15.152+2.058*BMI

20

2

R = 0.612
SEE = 3.6632

15
10
5
0
10

15

20

25

30

BMI
Figure 1. The BMI-%BF relationship of Japanese females

35

The BMI cut-off level for Japanese females

504

Table 2. A comparison of specificity and sensitivity of
the JASSO and the WPRO BMI cut-off points forobesity and overweight (at risk) in relation to estimated%BF using a whole-body DXA scan
The JASSO classification (%)1
%BF < 30%

%BF ≥ 30%

2

BMI < 25kg/m

98.9

91.1

2

1.1

BMI ≥ 25kg/m

The WPRO classification (%)

8.9
2%BF < 30%

%BF ≥ 30%

2

BMI < 23kg/m

94.7

60.0

2

5.3

40.0

BMI ≥ 23kg/m
1

The BMI classification proposed by the Japanese Society for the
Study of Obesity.
2
The BMI classification proposed by the Regional Office for theWestern Pacific Region of WHO, together with theInternational Association for the Study of Obesity (IASO) andthe International Obesity Task Force (IOTF).

Anthropometry
Anthropometry measurements include stature, body mass,eight skinfolds measurements (triceps, subscapular, biceps, iliac crest, supraspinale, abdominal, front thigh andmedial calf), five girths measurements (relaxed arm,
flexed and tensed arm, waist, gluteal and maximum calf),
and four bone breadths measurements (biacromial, biiliocristal, biepicondylar humerus and biepicondylar femur).
All sites were measured using the protocol of theInternational Society for the Advancement of Kinanthropometry (ISAK).24 The measurements were conducted bya Level 3 and a Level 1 anthropometrists who were accredited by ISAK and their technical error of measurements(TEM) were within the acceptable limits proposed
elsewhere.25 All measurement sites for each subject werelocated by the Level 3 anthropometrist prior to the measurements. From the measurements BMI, sum of eightskinfolds and height-corrected sum of eight skin-folds(sum of skinfolds*(170.18/stature)) were calculated.
All statistical analyses were conducted using the
SPSS® (version 10.05, 1999, Chicago) statistical package. A stepwise regression analysis was conducted to develop the regression equation using %BF results from
DXA scan as a dependent variable and BMI and age as
independent variables. In addition, cross-tabulation was
also used to assess specificity and sensitivity of different
BMI classifications. Based on previous recommendations26,27 %BF of 30% was used as a cut-off point ofobesity for Japanese females. The sensitivity and specificity results obtained from the JASSO classification wascompared with the results using the WPRO cut-off point.
Results
Results of body composition assessments using DXA andanthropometry are shown in Table 1. Figure 1 shows therelationship between BMI and %BF obtained from DXA
scan. The BMI-%BF relationship of Japanese young
females was determined by a stepwise regression analysis
using %BF as the dependent variable. While age wasinitially considered as an independent variable, it was excluded from the final model. The final equation was %BF= -15.152+2.058*BMI with R2=0.612 and SEE = 3.6632.
Using this equation, the BMI value at which thecorresponding %BF was 30% was calculated to be 21.9
(95%CI: 16.9kg/m2-28.6kg/m2). The results indicate apossible misclassification of Japanese females who have aconsiderable amount of body fat even though their BMI’s
are below 25, which the JASSO classification used as a
cut-off point of obesity.
Differences in magnitudes of misclassification between the JASSO and the WPRO classifications werecompared using sensitivity and specificity analysis (Table2). While the BMI value of 25kg/m2 has been used as a
cut-off point of “overweight” for the WHO classification
and “obese” for the JASSO classification, the current
study showed that 91% of Japanese females who had a%BF or more than 30% were classified as not overweightor obese using this value as a cut-off point. In comparison, a proportion of misclassified individuals reduced
to 60% when the BMI value of 23kg/m2, the cut-off pointof “overweight (at risk)” in the WPRO classification, wasused.
Discussion
Results from the current study showed that young Japanese females are likely to have a large amount of fat
deposition in relation to their BMI values. This is similar
to the pattern observed in young Japanese males28 andsupports previous findings that Asians have high %BF atlower BMI values when compared to Caucasian subjects.12,29 The stature and body mass of Japanese females
who participated in the current study were comparable tothe 20 years old age category of the 2002 NNS-J.15 Thissuggests that the current sample is typical of young
Japanese women and the current findings may represent
the normative trend of the BMI %BF relationship ofyoung Japanese females.
The current results showed that young Japanese females could have a considerable level of %BF at a relatively low BMI. Based on the JASSO classification, the
NNS-J conducted in 2002 reported only 7% of young Japanese females as “obese”. However the current findings
suggest that it is highly likely that there will be a higher
proportion of young Japanese females who should beclassified as “obese” and reported in the NNS-J. The
results obtained in the current study was consistent to theresult using Japanese males living in Australia30,
suggesting that young Japanese are likely to be misclassified if the BMI value of 25kg/m2 was used as a cutoff point of obesity.
The BMI value of 23kg/m2 that has been proposed as
the cut-off point of “overweight (at risk)” in the WPRO
classification13 and recently proposed as a one of the cutoff points to recommend public health action by WHO.14
From the results obtained from the current study it
appears that the BMI value of 23kg/m2 reflects actual
body fat level of young Japanese females better than the
BMI value of 25kg/m2 and therefore maximizes effectiveness of the BMI as a screening tool for the obesity for thisspecific population.

M Kagawa, K Uenishi, C Kuroiwa, M Mori and CW Binns

By saying that, still 60% of young Japanese females
were misclassified as “not obese” using the BMI value of
23kg/m2 as the cut-off point. This result illustrates a proportion of body fat deposition among young Japanese
females in relation to their body size and weight. Although the current study was unable to clarify the causesof the observed results, it is possible that strong preoccupation toward thinness and dieting behaviours without regular physical exercise are associating to the results.
There are Japanese studies that have focused on an issue
of “masked obesity”, which defined as a condition which
one has considerable amount of body fat without having
high BMI that classify the individual as “overweight” or“obese”.31 Although a phenomenon of “masked obesity”
could derived from inappropriate BMI cut-off points as in
the current study, some studies have suggested that an
attempt to lose body mass without regular physicalexercise has been suggested as one of the causes for“masked obesity”32 and a greater proportion of females
compared to males are “masked obese”.31 These previous
results may indicate a reliance of diet restriction as theirweight-loss method among young Japanese females andalso a possibility of depletion of muscle mass and increase in fat mass by experiencing repeated reduction andregaining of their body mass. As more than 50% of subjects with an excessive level of body fat were misclassified, it is possible that relatively large proportion ofyoung Japanese females may develop health problems attheir later stage of life.
Recently a Japanese committee that consists of members from eight medical societies, which include the
JASSO and the Japanese Society of Internal Medicine(JSIM), has proposed a screening guideline for a metabolic syndrome.33 The new guideline proposed using
waist circumference measured at the umbilical level with
cut-off points of 85cm for males and 90cm for females as
the standard criteria and individuals were classified as at
risk of metabolic syndrome if they have high waist circumference with any combination of high triglyceride orcholesterol levels, hypertension, or high blood glucose
levels. The effectiveness of waist circumference as anindex of cardiovascular disease risk has been suggested inseveral studies34-36 and the proposed waist circumference
values in Japan were based on the study using 1,193
subjects (418 women) that equate with a visceral fat areaof 100cm2, the value that considered as a cut-off point ofdeveloping coronary heart disease in Japanese.37 However, it is important to acknowledge that the females
participated in the study were mainly middle-aged (meanage: 55 ± 12 years) and it is unlikely for young Japanese
females to have a waist circumference of 90cm. The
average waist circumference value in the current study
was 66.3 ± 4.9cm and the range was 57.3-82.3cm. Although the definition of waist measurement site was notexactly the same, none of the subjects who had excessive
level of body fat in the current study had waist values≥90cm. Therefore it may be appropriate to determine
waist circumference level specifically for young Japanese
females and its application together with the appropriate
BMI cut-off point (i.e BMI value of 23kg/m2) in order toimprove detection of young Japanese females who require505

improvement in their lifestyle to reduce their health risks
later in their life.
The current study found that a considerable proportionof young Japanese females with an excessive amount ofbody fat are likely to being misclassified as not obeseusing the current classification used in the NNS-J. Future
research should be conducted on children and adolescents
to examine if the current classification is appropriate todetect individuals with childhood obesity in Japan. In
addition, the current study showed a wide 95% CI that
ranged from 16.9kg/m2 to 28.6kg/m2. In order to increase
the precision of the BMI %BF relationship as well as
sensitivity and specificity using different BMI cut-off
points, further studies using greater sample size may berequired.
Conclusion
This study aimed to assess sensitivity and specificity of
the BMI cut-off points that have been applied in the
National Nutritional Survey in Japan (NNS-J) for young
Japanese females based on the relationship between the
BMI and %BF. While the NNS-J reports a proportion ofobese individuals based on the BMI classification using
the value of 25kg/m2 as a cut-off point of “obese”, the
NNS-J report may misclassify young Japanese females
who are in fact obese. The current study suggests anapplication of lower BMI cut-off point would improvescreening ability of the BMI. The study also recommends
inclusion of body composition and fat distribution
assessments in a screening procedure to obtain precise
information of body fatness of individuals.

References
1. Obesity epidemic puts millions at risk from relateddiseases. http://www.who.int/archives/inf-pr-1997/en/pr9746.html.
2. Garn SM, Leonard WR, Hawthorne VM. Three limitationsof the body mass index. The American Journal of ClinicalNutrition 1986;44:996-997.
3. Ross WD, Crawford SM, Kerr DA, Ward R. Relationshipof the Body Mass Index with skinfolds, girths, and bonebreadths in Canadian men and women aged 20-70 years.
Am J Physical Anthropology 1988; 77: 169-173.
4. Stevens J, Cai J, Pumuk ER, Williamson DF, Thun MJ.
The effect of age on the association between body massindex and mortality. New Engl J Med 1998;338(1):1-7.
5. Yoshiike N, Nishi N, Matsushima S, Itou C, Ikeda Y,
Kashiwara H, Yoshinaga H, Ogura H, Komine S, Satou Y,
Satou N, Sasaki Y, Fujioka S, Oku J, Amamiya T, Sakata
T, Inoue S. Body mass index ni motozuku himan no teido
to tounyoubyou, kouketsuatsu, koushikesshou nokikeninshi tono kanren -tashisetsu kyoudou kenkyu ni yoru
ekigaku teki kentou- [Jap]. J Japan Soc Study Obesity
2000; 6 (1):4-17.
6. Wang J, Thompson JC, Russel M, Burastero S, Heymsfield
S, Pierson Jr. RN. Asians have lower body mass index(BMI) but higher percent body fat than do whites:
comparisons of anthropometric measurements. The Am J
Clin Nutr 1994;60:23-28.
7. Deurenberg P, Yap M, Staveren WAv. Body mass index
and percent body fat: a meta analysis among different
ethnic groups. Int J Obesity 1998; 22: 1164-1171.

506

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.
21.

22.

The BMI cut-off level for Japanese females
Deurenberg-Yap M, Schmidt G, Staveren WAv,
Deurenberg P. The paradox of low body mass index andhigh body fat percentage among Chinese, Malays andIndians in Singapore. Int J Obesity 2000; 24:1011-1017.
Lee ZSK, Critchley JAJH, Ko GTC, Anderson PJ, Thomas
GN, Young RP, Chan TYK, Cockram CS, Tomlinson B,
Chan JCN. Obesity and cardiovascular risk factors inHong Kong Chinese. Obesity Reviews 2002; 3:173-182.
Deurenberg P, Bhaskaran K, Lian PL. Singaporean Chineseadolescents have more subcutaneous adipose tissue thanDutch Caucasians of the same age and body mass index.
Asia Pac J Clin Nutr 2003; 12 (3): 261-265.
Chang C-J, Wu C-H, Chang C-S, Yao W-J, Yang Y-C, Wu
J-S, Lu F-H. Low body mass index but high percent body
fat in Taiwanese subjects: implications of obesity cutoffs.
Int J Obesity Related Metabolic Disorders 2003; 27 (2):
253-259.
Deurenberg P, Deurenberg-Yap M, Guricci S. Asians aredifferent from Caucasians and from each other in theirbody mass index/body fat per cent relationship. Obesity
Reviews 2002;3:141-146.
WHO/IASO/IOTF. Asia-Pacific perspective: Redefining
obesity and its treatment: Health Communications
Australia Pty Ltd; 2000.
WHO. Appropriate body-mass index for Asian populations
and its implications for policy and intervention strategies.
Lancet 2004; 363 (10): 157-163.
Kenkou Eiyou Jouhou Kenkyukai. Kokumin eiyou no
genjou-The National Nutrition Survey in Japan, 2002 [Jap].
1 ed. Tokyo: Daiichi Shuppan; 2004.
Matsuzawa Y, Inoue S, Ikeda Y, Sakata T, Saito Y, Satou
Y, Shirai K, Ohno M, Miyazaki S, Tokunaga K, Fukagawa
K, Yamanouchi K, Nakamura T. Atarashii himan no hantei
to himanshou no shindan kijun [Jap]. J Japan Soc Study
Obesity 2000; 6 (1):18-28.
Kajioka T, Ohsawa I, Yoshida T, Sato Y. Body andlifestyle characteristics in normal weight obesity (masked
obesity) in Japanese female high school students [Jap]. Jap
J School Health 1996; 38: 263-269.
Urata H, Tahara Y, Nishiyama K, Fukuyama Y,
Tsunawake N, Moji K, Yukawa K. Validity of various
obesity indices calculated from height and weight in adultfemales using the underwater-weighing method as areference [Jap]. Nihon Koushu Eisei zasshi 2000; 47 (8):621-629.
Takahashi R, Ishii M, Fukuoka Y. A method for evaluating
the masked obesity in young females [Jap]. Nihon Seiri
Jinrui Gakkaishi 2002;7(4):59-63.
NHMRC. National Statement on Ethical Conduct in
Research Involving Humans; 1999.
Heymsfield SB, Lichtman S, Baumgartner RN, Wang J,
Kamen Y. Body composition of humans: comparison of
two improved four-compartment models that differ in
expense, technical capacity, and radiation exposure. Am J
Clin Nutr 1990; 52: 52-58.
Wellens R, Chumlea WC, Guo S, Roche AF, Reo NV.
Body composition in white adults by dual-energy x-ray
absorptiometry. densitometry, and total body water. Am J
Clin Nutr 1994; 59:547-555.

23. Van Loan MD. Estimates of fat-free mass (FFM) bydensitometry, dual energy x-ray absorptiometry (DXA),
and bioimpedance spectroscopy (BIS) in Caucasian andChinese-American women. Applied Radiation and Isotopes
1998; 49 (5/6):751-752.
24. ISAK. International standards for anthropometricassessment. Canberra: ISAK; 2001.
25. Gore C, Norton K, Olds T, Whittingham N, Birchall K,
Clough M, Dickerson B, Downie L. Accreditation inanthropometry: an Australian model. In: Norton K, Olds T,
editors. Anthropometrica. Sydney: University of New
South Wales Press, 1996; 395-411.
26. Nagamine S. Hikashibou kara no himan no hantei [Jap].
Nihon Ishikai Zasshi 1972; 68 (9): 919-924.
27. Wilmore JH, Buskirk ER, DiGirolamo M, Lohman TG.
Body composition-a round table. The Physician and Sports
Med 1986; 14 (3):144-162.
28. Kagawa M, Kerr D, Uchida H, Binns C. Ethnic differencesin the BMI-%BF relationship: A comparative study ofJapanese and Australian Caucasian males. In: The 35th
Asia Pacific Academic Consortium for Public Health;
2003; Shanghai, China; 2003.
29. Deurenberg P. Universal cut-off points for obesity are notappropriate. Br J Nutr 2001;85:135-136.
30. Kagawa M, Kerr D, Binns C. Ethnic differences in the
BMI-%BF relationships between young Japanese andAustralian-Caucasian males living in Australia using dualenergy x-ray absorptiometry. Asia Pac J Public Health
2003; 15 (Suppl): S27-S32.
31. Fujise T, Nagasaki K. Characteristics of anthropometry andphysical fitness of masked obesity in young men andwomen [Jap]. Japanese J Physical Fitness and Sports Med
1999; 48: 631-640.
32. Suzuki H, Matsuo T. Jakunen josei ni okeru himando totaishibouritsu tono kanrensei [Jap]. Tairyoku Kagaku 1996;
45: 756.
33. Yakuji Nippo Limited. Proposal of guideline for metabolic
syndrome - eight medical societies including the JapaneseSocietyof Internal Medicine
involved[Jap].
http://www.yakuji.co.jp/contents/headlinenews/hln2005040
804.html.
34. Bei-Fan Z. Predictive values of body mass index and waist
circumference for risk factors of certain related diseases in
Chinese adults: study on optimal cut-off points of bodymass index and waist circumference in Chinese adults. Asia
Pac J Clin Nutr 2002; 11 (Suppl 8):S685-S693.
35. Dalton M, Cameron AJ, Zimmet PZ, Shaw JE, Jolley D,
Dunstan DW, Welborn TA. Waist circumference, waist-hip
ratio and body mass index and their correlation withcardiovascular disease risk factors in Australian adults. J
Int Med 2003; 254 (6): 555-63.
36. Welborn TA, Dhaliwal SS, Bennett SA. Waist-hip ratio isthe dominant risk factor predicting cardiovascular death inAustralia. Med J Australia 2003; 179(11-12):580-585.
37. The Examination Committee of Criteria for 'Obesity
Disease' in Japan. New criteria for 'obesity disease' inJapan. Circulation J 2002; 66 (11): 987-992.

M Kagawa, K Uenishi, C Kuroiwa, M Mori and CW Binns

507

Original Article

Is the BMI cut-off level for Japanese females for obesity
set too high? – A consideration from a body composition
perspective
Masaharu Kagawa PhD1, Kazuhiro Uenishi RD PhD2, Chiharu Kuroiwa RPT MSc3,
Miki Mori RD BSc2 and Colin W Binns MBBS MPH PhD1
12
3

School of Public Health, Curtin University of Technology, Perth, Australia
Kagawa Nutrition University, Saitama, Japan
Department of Physical Therapy, Koriyama Institute of Health Science, Fukushima, Japan

日本女性
從體組成的
日本女性肥胖的標準的
肥胖的標準的身體質量指數切點是否訂身體質量指數切點是否訂太高了
太高了?-從體組成的觀點來思考
本研究的主旨為評估已經被運用在日本國民營養調查(NNS-J)中的身體質量指數(BMI)切點，在年輕日本女性的敏感度跟特異度。使用雙能量 X 光吸收儀(DXA)
及體位測量評估 139 名年輕日本女性(18-27 歲)的 BMI 與體脂肪率(%BF)的相關。比較目前日本使用的 BMI 切點的敏感度跟特異度與建議使用於亞太族群的切點(WPRO 分類)。使用 DXA 掃描結果的數據去計算 BMI 與體脂肪率的相關，
得到的迴歸方程式為%BF=-15.152+2.058*BMI；R2=0.612，SEE=3.66。依照這個
方程式，當體脂肪率為 30%時所對應的 BMI 為 21.9 kg/m2 (95% CI=16.9-28.6)。
敏感度跟特異度分析發現，以 BMI 值為 25 kg/m2 當作肥胖的切點時，有超過90%體脂肪率>30%的日本女性被錯誤分類為非肥胖。當 BMI 值以 23 kg/m2 為切
點時，錯誤分組降低到 60%。此結果指出在 NNS-J 使用目前的分組可能無法確
實反映出年輕的日本女性的肥胖狀態，有一大部分身體囤積大量脂肪的女性將
被錯誤分組當為非肥胖者。本研究指出在裁定個體肥胖的程度時涵蓋詳細的體
組成測量的重要性。
關鍵字：身體質量指數、體脂肪、BMI 切點、日本人、女性。