Accuracy of Current Body Mass Index Obesity Classification for White, Black, and Hispanic Reproductive-Age Women

TLDR

The study compared NIH BMI‑based obesity classification to WHO percent‑body‑fat criteria among white, black, and Hispanic reproductive‑age women. Researchers measured weight, height, BMI, and DXA‑derived percent body fat in 555 healthy women aged 20–33 and evaluated the diagnostic accuracy of NIH BMI≥30 against WHO percent‑fat>35%. NIH BMI≥30 identified only 36.9% of women as obese versus 63.1% by WHO, with sensitivities of 47.8% (white), 75.0% (black), and 53.9%.

Abstract

To compare the National Institutes of Health's (NIH) body mass index (BMI)-based classification to identify obesity in comparison with the World Health Organization (WHO), which uses percent body fat, among white, black, and Hispanic reproductive-aged women.Body weight, height, BMI, and percent body fat (dual-energy X-ray absorptiometry generated) were determined for 555 healthy adult women aged 20-33 years (mean+/-standard deviation 26.5+/-4.0 years). Diagnostic accuracy of the NIH-based obesity definition (BMI of 30 kg/m or higher) was determined using the WHO criterion standard (percent body fat greater than 35%).Obesity as defined by the NIH (BMI 30 kg/m or higher) and by WHO (percent body fat greater than 35%) classified 205 (36.9%) and 350 (63.1%) of the women as obese, respectively. The NIH-defined obesity cutoff values had 47.8%, 75.0%, and 53.9% sensitivity in white, black and Hispanic, women, respectively. White and Hispanic women had 2.9% greater percent body fat than black women for a given BMI. Receiver operating characteristics curves analyses showed that the respective sensitivities improved to 85.6%, 81.3%, and 83.2%, and that 311 women (56.0%) were classified as obese as a whole when race or ethnic-specific BMI cutoff values driven by our data (BMI at or above 25.5, 28.7, and 26.2 kg/m for white, black, and Hispanic women, respectively) were used to detect percent body fat-defined obesity.Current BMI cutoff values recommended by the NIH failed to identify nearly half of reproductive-aged women who met the criteria for obesity by percent body fat. Using race or ethnic-specific BMI cutoff values would more accurately identify obesity in this population than the existing classification system.