Munich, Germany—The risk of cardiovascular (CV) and all-cause death is nearly 3 times higher in persons with normal weight who nevertheless have excess belly fat than in people who are overweight or obese with a high waist-to-hip ratio (WHR), according to new data presented by Karine Sahakyan, MD, PhD, MPH, a cardiologist at the Mayo Clinic, Rochester, MN, at the 2012 European Society of Cardiology Congress.
The study data came from a large, nationwide, representative sample of the US population, “so we’re pretty confident about the results of this study,” said Dr Sahakyan.
Normal-Weight Central Obesity Is Deadly
Nearly half (47.8%) of the people with a normal body mass index (BMI) had normal-weight central obesity, as defined by a high WHR.
The risk for CV death was 2.75 times higher and the risk for all-cause death was 2 times higher (hazard ratio, 2.08) in persons with normal-weight central obesity than in those with a normal weight and normal WHR. Persons with normal-weight central obesity had the highest risk of CV and all-cause deaths of the 6 subgroups studied. “From a public health point of view, this is very important,” Dr Sahakyan noted.
In obese persons with a normal WHR, the risk of CV mortality was 1.41 times higher compared with 2.34 times higher in obese persons with a high WHR, both compared with people with normal weight and normal WHR.
Previous studies have shown that central obesity is bad, Dr Sahakyan pointed out, but “this is the first study to show that even if a person has normal weight but with central adiposity, that person is at a higher risk of death.”
What to Look for
Dr Sahakyan and colleagues used National Health and Nutrition Examination Survey III data from 12,785 adults and matched baseline data to the National Death Index to obtain mortality status. People with cancer, chronic obstructive pulmonary disease, or those who were underweight were excluded. Over the long follow-up (median, 14.3 years), 2562 deaths were reported; of these, 1138 were CV related.
Participants were categorized by normal, overweight, and obese BMI and were further categorized by WHR using the World Health Organization criteria (normal, <0.85 in women and <0.90 in men; high, ≥0.85 in women and ≥0.90 in men).
Current guidelines do not include patients with normal BMI, so there is no requirement for lifestyle modification or measurement of WHR in these patients, Dr Sahakyan said. “Thus, these patients can be overlooked.”
Clinicians should pay greater attention to patients with normal-weight central obesity, including risk stratification and lifestyle interventions.
The WHR should be measured in all persons, even those with normal weight, she said, and she cautioned against relying on a visual assessment of fat distribution, which is very subjective.
Although the reasons that belly fat increases the risk of death are unknown and are being studied, Dr Sahakyan suggested 3 possible explanations. Visceral fat accumulation is a risk factor for diabetes and other CV risk factors, and inflammation is common among all of these. The amount of fat on the hips and legs and the muscle mass on the legs, which are known to be protective, are reduced in people with normal-weight central obesity compared with overweight and obese people.