Is BMI less important than belly size?

big belly of a fat man isolated on white

(CBS) Muffin tops and beer guts might be embarrassing, and a new study suggests that they can be deadly to boot. It shows that having a big belly ups the risk of death for patients with heart disease even if body mass index (BMI) falls in the healthy range.

Researchers at the Mayo Clinic analyzed data from almost 16,000 coronary artery disease patients around the world. They found that the death rate was two times higher for patients who packed extra weight in their midsections - what doctors call "central obesity" - than for their counterparts who carry their weight elsewhere in the body.

"People who have fat mostly in other locations in the body, specifically, the legs and buttocks, don't show this increased risk," study author Dr. Francisco Lopez-Jimenez, professor of medicine at the clinic, said in a written statement.

The study looked only at heart patients, but central weight is risky for everyone, experts say.

"Central fat is a real issue and increases risk of cardiovascular problems," Dr. Ken Fujioka, director of the Scripps Clinic Center for Weight Management, told CBS News in an email.

For years, doctors have been touting the importance of having a BMI within the healthy range - between 18.5 to 24.9 according to the Centers for Disease Control and Prevention. But the study seems to cast doubt on the importance of this simple gauge of body weight.

"BMI is just a measure of weight in proportion to height," study author Dr. Thais Coutinhho, a research fellow at the clinic, said in the statement. "What seems to be more important is how the fat is distributed on the body."

If BMI isn't the bottom line on risk, what is? Maybe a tape measure. In the study, patients with a healthy BMI faced a heightened risk when their waist measurements exceeded 33 inches (men) or 31 inches (women).

The study was published in the May 10 issue of the Journal of the American College of Cardiology.