BMI is Misleading, Study Finds

A new study was released Monday saying that the body mass index, which has been used for the past 180 years to determine if a person has a healthy or unhealthy weight, may be incorrectly classifying 50% of women and 20% of men as healthy when they are actually obese.

The study in the PLoS One journal suggested using a ratio of fat to lean muscle as the "gold standard" for detecting obesity and possible health problems instead of BMI.

The researchers used a costly diagnostic test called duel-energy X-ray absorptiometry, or DXA, and calculated the subject's level of obesity based on fat-composition standards used by the American Society of Bariatic Physicians.

The study's authors, Dr. Nirva R. Shah, New York's state commissioner of health, and Dr. Eric Braverman, a New York City internist in private practice, found that 20% of the study's men and 50% of the study's women shifted from normal and healthy into the obese column under the new measures. However, while the study found that more people should be classified as obese, it is hard to know whether the higher rates of obesity actually correlate to poorer health.

With the credibility of the BMI formula in question, researchers have proposed alternate ways of determining obesity including weight-loss counseling, exercise regimes and drug therapies. Simple measurements--waist circumference, hip circumference, hip-to-waist ratios--have also gained popularity as ways to distinguish between healthy and unhealthy weight.

The latest effort to calculate obesity was praised by experts who agree that the BMI is outdated and a poor way to measure a person's health, however they also said that the DXA scan, which measures bone density, may be too expensive for general use.

The study also looked at leptin, an appetite-boosting hormone secreted by the body's fat deposits, and found that it generally reflects an individual's fatness as determined by DXA. The study also showed that testing leptin levels may be a simpler and cheaper method of measuring obesity than DXA.

The study concludes by saying that physicians should also consider by taking routine measures of patients' leptin levels as an indicator of body composition and possibly a predictor of obesity-related diseases.

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