PhotoNot all fat, it seems, is created equal. Some is more harmful than others and the fat around the stomach is the most dangerous of all, according to researchers at the Mayo Clinic.

Their study found that people who are of normal weight but have fat concentrated in their bellies have a higher death risk than those who are obese. The subjects in the study who had a normal body mass index but central obesity -- a high waist-to-hip ratio -- had the highest cardiovascular death risk and the highest death risk from all causes.

"We knew from previous research that central obesity is bad, but what is new in this research is that the distribution of the fat is very important even in people with a normal weight," said senior author Francisco Lopez-Jimenez, M.D., a cardiologist at Mayo Clinic in Rochester, MN. "This group has the highest death rate, even higher than those who are considered obese based on body mass index. From a public health perspective, this is a significant finding."

Major study

The study included 12,785 people that comprised a representative sample of the U.S. population. Over the course of the study there were 2,562 deaths, with 1,138 of them cardiovascular related.

The risk of cardiovascular death was 2.75 times higher, and the risk of death from all causes was 2.08 times higher, in people of normal weight with central obesity, compared with those with a normal body mass index and waist-to-hip ratio.

Why belly fat is particularly deadly isn't immediately clear. Researchers say it may be related to a "higher visceral fat accumulation" in this group, which is associated with insulin resistance and other risk factors. Other types of fat is known to provide some protective elements. With less of the "protective fat" the visceral fat around the belly is even more dangerous.

Takeaway lesson

The take away from the research, the scientists say, is knowing your body mass index (BMI) isn't enough. It's also important to know that a normal BMI doesn't mean heart disease risk is low.

Getting a waist-to-hip measurement can tell you where on your body fat is distributed and can tell you if you are at risk, even if you have what is considered normal body weight.

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