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Study: US obesity rates may be more severe than previously thought

A new study has found that the widespread use of the body mass index to determine obesity has caused doctors to downplay the issue.

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Seventeen year-old Marissa Hamilton stands on a scale during her weekly weigh-in at the Wellspring Academy in Reedley, California, a special school that helps teens and college level students lose weight along with academic courses. According to the Centers for Disease Control and Prevention, 16 percent of children in the US ages 6-19 years are overweight or obese, three times as many since 1980. (Justin Sullivan/AFP/Getty Images)

Obesity in the United States may be even worse than initially believed, according to a new study in PLoS One journal

According to the study's findings, the widely used body mass index (BMI), a measure of body fat based on height and weight, has allowed the US to underestimate its obesity crisis. A BMI between 25 and 30 is classified as overweight, and 30 or more as obese. 

However, researchers at the New York University School of Medicine and the Weill Cornell Medical College found that 39 percent of people whose BMI puts them in the overweight category would be considered obese if their body fat percentage were considered, according to US News and World report

"The Body Mass Index is an insensitive measure of obesity and prone to under-diagnosis, while direct fat measurements are superior because they show distribution of body fat," said Dr Eric Braverman, the study's lead author, according to BBC News. "Some people call it the 'baloney mass index.'" 

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Using a dual-energy X-ray absorptiometry (DEXA) scan to measure body fat, muscle mass and bone density, the researchers looked at the BMI and body fat measurements of 1,393 participants, BBC News reported.

The data showed that most of the time the two measures came to the same conclusion, but 539 people (almost one in four) in the study were not labeled obese according to BMI, though their fat percentage suggested they were.

"Roughly 30 percent of Americans are obese, but when you use other methods, closer to 60 percent are obese," Dr Braverman said, the International Business Times reported.  

BMI is even more unreliable for women then men, IBT reported, possibly because women lose their muscle mass faster as they age than men do. Almost half of the women tested were considered overweight by BMI, but obese by body fat percentage, compared to only a fourth of the men surveyed, according to IBT. 

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Under BMI classifications, bodybuilders can be classified as obese based on their body mass index, 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," Dr Braverman told Health.com

Dr Braverman and his team suggested the three-pronged approach of lowering BMI obesity cutoffs, using DXA scans when possible, and incorporating leptin tests to reduce the health risks obesity poses.

"Making these changes now can save the US a fortune down the road, if it allows us to alert more people to their risks and prevent them from getting worse," he said, Health.com reported. 

http://www.globalpost.com/dispatch/news/health/120403/study-us-obesity-rates-may-be-more-severe-BMI