MONDAY, April 2, 2012 (Health.com) — Doctors and health officials have relied for decades on body mass index (BMI), a ratio of height to weight, to categorize people as overweight and obese. A new study, however, suggests the use of BMI may be leading us to underestimate the already sky-high obesity rate.
BMI, the researchers say, is an overly simplistic measure that often misrepresents physical fitness and overall health, especially among older women. Nearly 4 in 10 adults whose BMI places them in the overweight category would be considered obese if their body fat percentage were taken into account, according to the study.
“Some people call it the ‘baloney mass index,’” says lead author Eric Braverman, M.D., president of the Path Foundation, a nonprofit organization in New York City dedicated to brain research. Bodybuilders can be classified as obese based on their BMI, he says, while “a 55-year-old woman who looks great in a dress could have very little muscle and mostly body fat, and a whole lot of health risks because of that—but still have a normal BMI.”
Based on their findings, Braverman and his coauthor, New York State Commissioner of Health Nirav Shah, M.D., say the BMI threshold for obesity, which now stands at 30, should be lowered to 24 for women and 28 for men. By that standard, a 5-foot 6-inch woman and a 5-foot 11-inch man would be considered obese at about 150 and 200 pounds, respectively.
The study participants—patients at a specialized private health clinic in Manhattan—aren’t typical of the population as a whole, Braverman notes. Still, he says, the large discrepancy between BMI and body fat measures seen in the study suggest that BMI guidelines should be revisited.
“People aren’t being diagnosed [as obese], so they’re not being told about their risk of disease or being given instruction on how to improve their health,” says Braverman, who is also a clinical assistant professor of neurosurgery at Weill Cornell Medical College, in New York City.
Next page: Lowering obesity cutoff could cause problems