Blew, Robert M., Sardinha, Luis B., Milliken, Laura A., Teixeira, Pedro J., Going, Scott B., Ferreira, Dawna L., Harris, Margaret M., Houtkooper, Linda B., and Lohman, Timothy G.
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. Research Methods and Procedures:Three hundred seventeen healthy, sedentary, postmenopausal women (ages, 40 to 66 years; BMI, 18 to 35 kg/m2; 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/m2. 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. Discussion: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/m2rather than BMI >30 kg/m2may be superior for diagnosing obesity in postmenopausal women.