As if the nations weight problems were not daunting enough, a new study has found that the body mass index, the 180-year-old formula used to distinguish between healthy and unhealthy weight, may be incorrectly classifying about half of women and just over 20% of men as being the picture of health when their body-fat composition suggests they are obese.

The study, published Monday in the journal PLoS One, uses a patients ratio of fat to lean muscle mass as the “gold standard” for detecting obesity and suggests that it could be a better bellwether of an individuals risk for health problems.

The researchers suggested that body fat would predict individuals health risks better than the BMI. To measure fatness, they used a costly diagnostic test called dual-energy X-ray absorptiometry, or DXA, and calculated subjects level of obesity based on fat-composition standards used by the American Society of Bariatric Physicians.

The results also suggest that the BMI is a poor measure of fatness in men — but not always in a way that underestimates their obesity. In all, 20% of the studys men shifted from normal and healthy into the obese column under the new measure. But far more frequently than was the case among women, men who were obese by the BMI standard were reclassified as normal and healthy when they were measured with the DXA.

Though men fared better than women under the proposed new standard, the resulting picture is uniformly grim, according to the studys authors, Dr. Nirav R. Shah, New Yorks state commissioner of health, and Dr. Eric Braverman, a New York City internist in private practice.

Fat Thanks to Sona S. for the tip!

Americans may be more obese than they think, researchers say – latimes.com