People who had the highest cardiovascular death risk and the highest death risk from all causes were those who had central obesity with a normal body mass index (BMI), or a high waist-to-hip ratio.
Francisco Lopez-Jimenez, M.D., senior author and a cardiologist at Mayo Clinic in Rochestor, explained:
"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. 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."
Researchers examined data from the Third National Health and Nutrition Examination Survey, a representative sample of the U.S. population, which included 12,785 people aged 18 and older.
The survey provided experts with body measurements, including height, weight, hip and waist circumference, as well as comorbidities, socioeconomic status, and physiological and laboratory measurements. In order to assess deaths at follow-up, baseline data were matched to the National Death Index.
People examined were divided by BMI into 3 categories:
- normal- 18.5 to 24.9 kg/m2
- overweight- 25.0 to 29.9 kg/m2
- obese- Greater than 30 kg/m2
- normal- <0.85 in women and <0.90 in men
- high- e0.85 in women and e0.90 in men
The mean age of those studied was 44, 47.4% percent were men, and the median follow up period was 14.3 years. There were 2,562 deaths recorded, of which 1,138 were cardiovascular related.
Analysis showed that the risk of death from all causes was 2.08 times higher, and the risk of cardiovascular death was 2.75 times higher, in people with central obesity who had normal weight, compared to those with a normal BMI and waist-to-hip ratio.
Karine Sahakyan, M.D., Ph.D., a cardiovascular research fellow at Mayo Clinic in Rochester, said:
"The high risk of death may be related to a higher visceral fat accumulation in this group, which is associated with insulin resistance and other risk factors, the limited amount of fat located on the hips and legs, which is fat with presumed protective effects, and to the relatively limited amount of muscle mass."
Dr. Lopez-Jimenez wants readers to understand that even though their body mass index might be normal, it doesn't mean they have a low risk of heart disease. People can determine their risks by getting a waist-to-hip measurement, because where fat is distributed on the body can tell a lot, even if people have normal body weights.