BMI Does Not Properly Define Obesity in Postmenopausal Women

A recent study has shown that a BMI cut-point of 30 kg/m² may not be an appropriate indicator of obesity status in postmenopausal women.

Although BMI is a widely used indicator of obesity status, there are concerns about the validity of the measurement in postmenopausal women.
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For their study, researchers collected data from 1329 postmenopausal women who participated in the Buffalo OsteoPerio Study. Obesity was defined as having a BMI of 30 kg/m² or higher, and a body fat percent greater than 35%, 38%, or 40%. The researchers calculated sensitivity, specificity, and positive and negative predictive value in order to evaluate the validity of BMI-defined obesity.

Overall, the sensitivity of BMI-defined obesity was 32.4% for 35% body fat, 44.6% for 38% body fat, and 55.2% for 40% body fat. Specificity values were 99.3%, 97.1%, and 94.6%, respectively.

The empirical optimal BMI cut-point to define obesity was 24.9 kg/m² for 35% body fat, 26.49 kg/m² for 38% body fat, and 27.05 kg/m² for 40% body fat according to analyses with Youden's J index.

“Results demonstrate that a BMI cut-point of 30 kg/m² does not appear to be an appropriate indicator of true obesity status in postmenopausal women. Empirical estimates of the validity of BMI from this study may be used by other investigators to account for BMI-related misclassification in older women,” the researchers concluded.

—Michael Potts

Reference:

Banack HR, Wactawski-Wende J, Hovey KM, Stokes A. Is BMI a valid measure of obesity in postmenopausal women? [published online November 13, 2017]. Menopause. doi: 10.1097/GME.0000000000000989.