Is the current BMI obesity classification appropriate for black and white postmenopausal women?
OBJECTIVE
To evaluate the relation between body fatness (%Fat) and body mass index (BMI) and to evaluate the validity of the BMI standards for obesity established by the NIH in older black and white postmenopausal women.


METHODS
Height, weight, BMI, and %Fat, assessed by DXA, were determined for 296 healthy, independently living women ranging in age from 50 to 80 years (M+/-s.d.; 64.4+/-7.8 years).


RESULTS
Per NIH guidelines, 32% were classified as obese (> or = 30 kg/m2, mean BMI = 28.1+/-5.5 kg/m2). In contrast, using the %Fat criterion of 38% advocated by Lohman to define obesity, 47% of our sample was obese (mean %Fat=37.3+/-6.2%). A moderately high curvilinear relation existed between BMI and %Fat (R = 0.82, SEE = 3.57 %Fat, P<0.05). Race added meaningfully to the prediction of %Fat (P<0.05) such that for the same BMI, black women will have 1% lower body fatness than white women. Based on a %Fat > or = 38 as the criterion for obesity, receiver operating characteristic (ROC) analysis, performed separately by race, indicated that the currently accepted BMI cutpoint for obesity produced low sensitivity (69% and 61% for black and white women, respectively). Alternatively, BMI values > or = 28.4 kg/m2 for black women and > or = 26.9 kg/m2 for white women to define obesity maximized classification accuracy.


CONCLUSIONS
We conclude that current BMI categories may not be appropriate for identifying obesity among postmenopausal women. Furthermore, the relation between BMI and %Fat is different in black compared to white women but remains constant from the sixth through the eighth decade of life.
Evans
E M
EM
Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana 61801, USA. elevans@uiuc.edu
Rowe
D A
DA
Racette
S B
SB
Ross
K M
KM
McAuley
E
E
D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D044383:Black People; D001823:Body Composition; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000145:classification* / Q000208:ethnology* / Q000503:physiopathology; D017698:Postmenopause / Q000378:metabolism; D012372:ROC Curve; D012680:Sensitivity and Specificity; D044465:White People