(HealthDay) -- Standard definitions of obesity, which are based on height and weight, may not apply to former National Football League players and other groups with greater muscle mass, according to a new study.
"We found [body-mass index] to overestimate the number of obesity cases in a population of retired professional football athletes," Dr. Mark Hyman and colleagues from the University of California, Los Angeles, said in a news release from the American College of Occupational and Environmental Medicine.
The study was published in the July issue of the Journal of Occupational and Environmental Medicine.
Critics of the widespread use of BMI to determine obesity have noted that highly fit athletes such as New England Patriots quarterback Tom Brady would be considered overweight using that measurement alone.
Researchers compared several measures of obesity among a group of nearly 130 former NFL players who had retired up to 32 years before the study began. Based on the standard definition of obesity -- having a BMI of 30 or higher -- 67 percent of the players would be considered obese.
The former players also underwent a test called dual-energy X-ray absorptiometry, or DEXA, to provide a detailed measurement of their fat and lean body mass. The researchers noted the DEXA cutoff point for obesity is 25 percent body fat, or 27 percent for those older than 40. Based on this measure, only 13 percent of the retired athletes were classified as obese.
The study concluded that DEXA may provide a more accurate measure of obesity in this unique population. The researchers also argued that raising the BMI cutoff from 30 to 40 would be a more appropriate definition of obesity among retired football players. They noted, however, that a BMI of 40 or more for the general population would be an indication of severe obesity.
The longer a player's NFL career, the more likely they were to be obese by either definition, the researchers found. Those with a BMI of 30 or more also were more likely to have obstructive sleep apnea, a common obesity-related condition. More research is needed on obesity risks and prevention among NFL players, the study authors said.
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The U.S. Centers for Disease Control and Prevention provides information on obesity.