Accuracy of BMI as a Measurement of Obesity in Postmenopausal Women

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Substantial proportion of older women who are truly obese are misclassified as nonobese by BMI.
Substantial proportion of older women who are truly obese are misclassified as nonobese by BMI.

Body mass index (BMI) at a cut-point of 30 kg/m2 may not be an appropriate indicator of obesity in postmenopausal women, according to a study published in Menopause. 

Researchers identified and analyzed retrospectively data from 1329 postmenopausal women, ranging in age from 53 to 85 years, who were participating in the Buffalo OsteoPerio Study. The validity of BMI-defined obesity relative to body fat percent was evaluated by calculating the sensitivity, specificity, positive predictive value, and negative predictive value of data.

Study results showed a sensitivity and specificity of BMI-defined obesity for 35%, 38%, and 40% body fat to be 32.4%, 44.6%, 55.2% and 99.3%, 97.1%, 94.6%, respectively. The empiric optimal BMI cut-points to define obesity for 35%, 38%, and 40% were found to be 24.9 kg/m2, 26.49 kg/m2, and 27.05 kg/m2

Researchers concluded that a BMI cut-point of 30 kg/m2 is too high and not an accurate indicator of obesity in postmenopausal women. Such inaccuracies can lead to a bias in assessing obesity and ultimately health outcomes in postmenopausal women. Further, the authors recommend BMI cut-points of 24.9, 26.5, or 27.1 kg/m2, which were found in this study to be optimal BMI cut-points based on their correlation to body fat percent of 35%, 38%, and 40%.

Reference

Banack H, 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

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