Study Suggests BMI Scale Is Weighted Against African Americans

Tuesday, April 14, 2009

The body mass index (BMI) formula that is widely used to determine body fat may not be accurate for non-Caucasians, a study published last week in the British Journal of Nutrition found.

"This scale was created years ago and is based on Caucasian men and women," said Molly Bray, one of the study's researchers and an associate professor of pediatrics at Baylor College of Medicine in Houston. "It doesn't take into account differences in body composition between genders, race/ethnicity groups and across the life span."

Bray and her colleagues are using another method, a low-dose X-ray called DXA, to estimate bone density, lean mass and fat mass.

Based on the DXA reading, the researchers found that an African American woman, for example, may not be overweight or obese even though the BMI formula, which considers a person's height and weight, indicates that she is.

"Right now non-Hispanic white women are not considered obese until they have a BMI of 30 or above," said Bray. "For African American women the number to cross is around 32." Women in some other racial and ethnic groups were considered obese even if their BMI number was below 30.

The results were similar in men.

The discrepancies, Bray said, are due to variations in bone mineral content, hydration state and the density of lean mass in different ethnic groups.

-- Sindya N. Bhanoo

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