MONDAY, Nov. 9, 2015 (HealthDay News) -- Can belly fat be a problem even for people who aren't overweight? New research says yes, excess weight around the middle boosts the risk of premature death even for people considered normal weight.

What's more, normal weight people with excess stomach fat had an even higher risk of dying early than overweight or obese people did, according to new research published online Nov. 10 in the Annals of Internal Medicine.

"Belly fat is bad fat," said Dr. Paul Poirier, from the Institute of Cardiology at Laval University in Quebec, Canada, and the author of an accompanying editorial in the same issue of the journal.

Stomach fat has been linked to high cholesterol, inflammation, heart disease, stroke and diabetes, he explained.

"When you have fat around the belly, it's a lot worse than having the same amount of fat around the hip," Poirier said. "If your weight is normal, but you have weight around the middle, it's bad. If you've got a belly above 40 inches for men and 34 inches for women, this is obesity [even if your weight measurements seem normal]," Poirier said.

These people may not be obese from a weight perspective, but they are obese from a waist perspective, he said.

For the study, a team led by Dr. Francisco Lopez-Jimenez, a professor of medicine at the Mayo Clinic in Rochester, Minn., used data from a national survey to compare the risk of premature death among more than 15,000 adults. The mean follow-up time was 14 years.

The researchers looked at body mass index (BMI), a rough estimate of body fat based on weight and height measurements. They also looked at waist-to-hip ratios.

The investigators found that normal weight adults with extra stomach fat had the worst long-term survival, regardless of BMI. And, normal weight men with bigger bellies seemed to fare even worse than slender women with more tummy fat.

A normal weight male with more fat around the waist had an 87 percent increased risk of death during the study period compared to a man who was normal weight without extra belly fat. Compared to overweight or obese men (as measured solely by BMI, without specific waist size information), a normal weight man with extra belly fat had more than twice the risk of dying early, the study revealed.

Normal weight women with extra belly fat had nearly a 50 percent increased risk of death during the study period versus a normal weight woman whose weight was more equally distributed throughout her body. Compared to obese women (measured by BMI only), the normal weight women with belly fat had a 32 percent higher risk of early death, the researchers found.

Dr. David Katz, director of the Yale University Prevention Research Center, in New Haven, Conn., and president of the American College of Lifestyle Medicine, said the study findings raise the question: who would have more belly fat and still be at a normal weight according to their BMI?

Some people are more prone to depositing excess fat around the middle, he said. This can lead to fat accumulation in vital organs, especially the liver, he explained.

Another group may be those who have excess body fat and illness, perhaps in early stages, causing loss of lean body mass, Katz said. Although it's not clear from this study how many people might fall into this category, he added.

Regardless of why someone has gained weight around the middle, Katz said, "We have long known that all varieties of overweight are not created equal with regard to health risk, and that central obesity is the most concerning variety."

In his editorial, Poirier wrote, "These new data provide evidence that clinicians should look beyond BMI. Although assessing for total fat mass with BMI to identify patients at greater cardiovascular risk is a good start, it is not sufficient."

More information

For more information on obesity, visit the U.S. Centers for Disease Control and Prevention.