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Athlete Study Exposes Flaw of BMI Obesity Measure

Last week it was obese football players. Now it's ... overweight basketball players?

Yep. If you apply a widely used criterion to the published heights and weights of NBA players, nearly half qualify as overweight.

Only four players assessed using the body-mass index (search) by The Associated Press made it all the way to the "obese" range, most notably — you guessed it — Miami Heat star Shaquille O'Neal.

But the notion that 200 other NBA players out of 426 are even within a 3-point shot of tubby might make one wonder: Just how good is the BMI at telling if somebody is too fat?

The finding follows a study of football players published last week in the Journal of the American Medical Association. That research concluded that according to BMI standards, more than half of National Football League players are obese, and nearly all are overweight. The study's validity was questioned by an NFL spokesman.

What's going on here? Obesity (search) experts say the BMI really is a useful guide to identifying individuals who are too fat for their own good, but it shouldn't be used by itself.

"The value of the BMI for the (general) population is it's a good first step, and I underline 'first step,"' says Dr. George Bray of the Pennington Biomedical Research Center in Baton Rouge, La.

"No one has ever suggested it's the only criterion to use, because it clearly is not."

The body-mass index doesn't directly measure fat. It comes from a formula that considers only weight and height. At 7-foot-1 and 325 pounds, O'Neal had the NBA's highest BMI, 31.6, in the AP analysis. (He admits to gaining 2 pounds since those numbers were posted.)

That puts him in the "obese" range, which is 30 and above. A BMI indicates normal weight if it falls between 18.5 and 24.9, and overweight if it's between 25 and 29.9.

"I've read that same formula, but as an athlete, I'm classified as phenomenal," O'Neal told The AP. "You can look it up."

O'Neal, ranked among the NBA's 50 greatest players, lost 40 pounds after team management asked him to when he joined the team last summer. He says he now has 13 percent body fat.

Studies show that as a group, people who score "overweight" on the BMI run an elevated risk of developing such problems as diabetes and heart disease, while those in the "obese" category have even higher risks.

Tim Frank, the NBA's vice president of basketball communications, said BMI studies like the AP's analysis are "pretty subjective" and weight has not been an issue in the league.

"We're confident our players are some of the best-conditioned athletes in the world," he said.

Nationally, almost a third of American adults are obese and nearly two-thirds are either obese or overweight under the BMI criteria. Experts are studying how appropriate the standard cutoffs are for non-Caucasians; research suggests that members of many Asian populations may need to keep their weight lower to fend off health risks.

The AP's basketball analysis points out a key drawback of the BMI: People who are lean but well muscled, like most basketball players, can have the same elevated BMI as somebody who carries too much fat.

You might think that somebody who gets an "overweight" BMI from muscle would have a lower health risk than somebody of the same BMI, but carrying more fat. But experts say that's not clear. For one thing, experts noted, athletes tend to keep their high BMI's after they retire — only then, their muscle gets replaced by fat.

For non-Asians, BMI's are informative when they're below 25 or above 30, says Dr. Robert H. Eckel of the University of Colorado, president-elect of the American Heart Association. For example, a BMI of 23 likely indicates an acceptable amount of body fat while one of 33 means "you've got too much fat," he said.

But for BMI's between 25 and 30 — basically the overweight range — the implication is more murky, especially in athletic people, he said.

He and others emphasize that calculating BMI is really just a starting point. A key follow-up is determining waist size with a measuring tape. If it's greater than 40 inches in a man or more than 35 inches in a woman, there's an elevated risk of weight-related disease.

Some studies suggest the waist measurement tracks health risks better than BMI, said Dr. Louis Aronne, president of the North American Association for the Study of Obesity. But like other experts, he thinks "the two of them together provide you with the best information."

And, Bray adds, it's important to look at other things like a person's age, level of physical activity, rate of weight gain, blood pressure and cholesterol levels to really get a good picture of one's risk.

In any case, Dr. William Dietz of the federal Centers for Disease Control and Prevention, said BMI alone is a good enough tool that the national estimate of obese adults — about 59 million people — won't be affected by findings from the specialized world of professional athletes.

And for those who persist in thinking Shaquille O'Neal is obese, he has a simple message: "You think that, stick to science. Top 50, three rings, lot of money, two mansions."