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BMI Often Fails to ID Obesity in Women of Reproductive-Age

When researchers use race-, ethnic-specific body mass index cutoffs, sensitivities improve

THURSDAY, April 29 (HealthDay News) -- Using cutoff values for body mass index (BMI) that are recommended by the National Institutes of Health (NIH) may fail to identify obesity in reproductive-aged women in certain ethnic or racial populations who meet the criteria for obesity by percent body fat, according to research published in the May issue of Obstetrics & Gynecology.

Mahbubur Rahman, M.D., and Abbey B. Berenson, M.D., of the Center of Interdisciplinary Research in Women's Health in Galveston, Texas, determined the body weight, height, BMI and body fat percentage of 555 black, white and Hispanic women, aged 20 to 33, to compare the NHI BMI-based classification of obesity with the body fat percentage-based criteria used by the World Health Organization.

The researchers found that, using BMI of 30 kg/m2 or higher and body fat percentage of 35 or higher, 205 (36.9 percent) and 350 (63.1 percent) of the women were classified as obese, respectively. At a given BMI, white and Hispanic women had 2.9 percent more body fat than black women. Sensitivity improved when race or ethnic-specific BMI cutoff values were used. The NIH's cutoff values had a sensitivity of 47.8, 75.0 and 53.9 percent in white, black and Hispanic women, respectively. When the researchers used race- or ethnic-specific BMI cutoffs determined by their data (at or above 25.5, 28.7 and 26.2 kg/m2), they found that the sensitivities in the three groups were 85.6, 81.3 and 83.2 percent, respectively.

"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," the authors write.

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