"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 normal weight," said Francisco Lopez-Jimenez, senior study author and cardiologist at the Mayo Clinic in Rochester, Minnesota.
"This group has the highest death rate, even higher than those who are considered obese based on BMI, a height to weight ratio. From a public health perspective, this is a significant finding," said Lopez-Jimenez, according to a Mayo statement.
The study included 12,785 subjects aged 18 and above from the third National Health and Nutrition Examination Survey (NHANES III) and provided a representative sample of the US population.
The surveys recorded body measurements such as height, weight, waist circumference and hip circumference, as well as socio-economic status, physiological and lab measurements.
Subjects were divided into three categories of BMI -- normal, overweight and obese -- and two categories of waist-to-hip ratio in women and men. The mean age of subjects was 44 years and 47.4 percent were men.
The median follow up period was 14.3 years. There were 2,562 deaths, of which 1,138 were related to cardiovascular issues.
The subjects with normal BMI but central obesity as defined by the belly fat had the highest cardiovascular death risk and the highest death risk from all causes among all subgroups.
The risk of cardiovascular death among those with belly fat was 2.75 times higher and the risk of death from all causes was 2.08 times higher in normal weight obese people as compared with subjects with normal BMI and normal waist-to-hip ratio.
"To our knowledge, it is the first study that evaluated nationwide estimates of death in central obesity even in the absence of obesity as measured by BMI," said Karine Sahakyan, cardiology research fellow at the Mayo Clinic in Rochester.
These findings were presented at European Society of Cardiology Congress 2012. - KT
