A beer belly is a dangerous thing.
A new analysis of data from a large national study has found that carrying fat around the middle of the body greatly raises the risk for heart disease and death, even for those of normal weight.
Doctors usually determine obesity by body mass index, or B.M.I. —calculated from height and weight — but the calculation does not distinguish between fat and lean muscle weight. Measuring waist-to-hip ratio presents a different, and possibly more accurate, picture because it accounts for central obesity, or visceral fat, the fat stored around the internal organs.
Waist-to-hip ratio is waist measurement divided by hip measurement. According to the World Health Organization, a ratio higher than .90 for men or .85 for women defines central obesity.
It has been known for some time that having an “apple” shape increases the risk for disease and death. But the new study found that a man of normal B.M.I. with an abnormally large belly has an 87 percent higher risk for death than a man with the same B.M.I. but a normal waist-to-hip ratio. Pot-bellied women of normal B.M.I. have a 48 percent higher risk than women with normal B.M.I. and normal belly fat.
Researchers used data on 15,184 men and women older than 18 who were examined at mobile examination centers. They followed them for an average of more than 14 years, during which there were 1,404 deaths from cardiovascular diseases. The association of waist-to-hip ratio with increased risk persisted even after controlling for smoking, history of heart attack or diabetes, race, poverty, blood lipid levels and other factors.
The study, in Annals of Internal Medicine, found that people with normal weight and central obesity have worse long-term survival than anyone of any weight with normal fat distribution. For example, compared with an overweight or obese man with normal waist-to-hip ratio, men of normal weight with central obesity were at more than twice the risk for death, which may help to explain the “obesity paradox,” in which obesity seems to protect against heart disease in some people.
“People with normal weight according to B.M.I. can’t be reassured that they don’t have any fat-related health issues,” said the senior author, Dr. Francisco Lopez-Jimenez, a professor of medicine at the Mayo Clinic. “Having a normal weight is not enough. It’s good only if the distribution of fat is healthy.”
Correction: November 10, 2015
An earlier version of this post erroneously included diabetes among the conditions that carrying fat around the middle of the body raises the risk of, according to the new study. While diabetes has been shown to be associated with a beer belly in earlier studies, in this study diabetes was a variable they controlled for.