Assessing the validity of body mass index standards in early postmenopausal women.
OBJECTIVE
To examine the relationship between percentage of total body fat (%Fat) and body mass index (BMI) in early postmenopausal women and to evaluate the validity of the BMI standards for obesity established by the NIH.


METHODS
Three hundred seventeen healthy, sedentary, postmenopausal women (ages, 40 to 66 years; BMI, 18 to 35 kg/m(2); 3 to 10 years postmenopausal) participated in the study. Height, weight, BMI, and %Fat, as assessed by DXA, were measured. Receiver operating characteristic analysis was performed to evaluate the ability of BMI to discriminate obesity from non-obesity using 38%Fat as the criterion value.


RESULTS
A moderately high relationship was observed between BMI and %Fat (r = 0.81; y = 1.41x + 2.65) with a SE of estimate of 3.9%. Eighty-one percent of other studies examined fell within 1 SE of estimate as derived from our study. Receiver operating characteristic analysis showed that BMI is a good diagnostic test for obesity. The cutoff for BMI corresponding to the criterion value of 38%Fat that maximized the sum of the sensitivity and specificity was 24.9 kg/m(2). The true-positive (sensitivity) and false-positive (1--specificity) rates were 84.4% and 14.6%, respectively. The area under the curve estimate for BMI was 0.914.


CONCLUSIONS
There is a strong association between %Fat and BMI in postmenopausal women. Current NIH BMI-based classifications for obesity may be misleading based on currently proposed %Fat standards. BMI >25 kg/m(2) rather than BMI >30 kg/m(2) may be superior for diagnosing obesity in postmenopausal women.
Department of Physiology, University of Arizona, Tucson, Arizona 85721, USA.
Robert M
RM
Blew
Luis B
LB
Sardinha
Laura A
LA
Milliken
Pedro J
PJ
Teixeira
Scott B
SB
Going
Dawna L
DL
Ferreira
Margaret M
MM
Harris
Linda B
LB
Houtkooper
Timothy G
TG
Lohman
D015502:Absorptiometry, Photon; D000273:Adipose Tissue; D000328:Adult; D000368:Aged; D001823:Body Composition; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D005260:Female; D006801:Humans; D008875:Middle Aged; D009316:National Institutes of Health (U.S.); D009765:Obesity / Q000175:diagnosis*; D017698:Postmenopause; D012372:ROC Curve; D012680:Sensitivity and Specificity; D014481:United States