Lose Belly Fat to Save Your Heart

En español | A big belly is bad for your heart, but which kind of diet — low-fat or low-carb — is best for taking off those extra pounds?

According to new research, while both can help trim your waistline, one works markedly better than the other.

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Want to make sure you lose extra pounds? Pick a diet that you can stick with long term. — Photo by Rubberball/Getty Images

In a six-month weight-loss study, researchers at Johns Hopkins University found that participants who followed a low-carb diet lost an average of 29 pounds — 10 pounds more than the average loss of 19 pounds for those on a low-fat diet. The low-carb group also did just as well as the low-fat group on a blood-flow test that measures how well arteries expand, a mark of cardiovascular health.

Research shows that low-carb diets improve blood pressure and levels of HDL cholesterol (the "good" kind), says lead investigator Kerry Stewart, professor of medicine and director of clinical and research exercise physiology. But there have been concerns that low-carb diets are bad for the heart. When people cut down on carbs — meaning sugars and starches — they tend to eat more fat, which may have a harmful effect on cardiovascular health. Yet after six months, "we saw an improvement in blood-vessel health on both diets," says Stewart, "and the amount of improved blood flow was directly linked to how much belly fat the individuals lost. According to several measures we made, the low-carb group lost more belly fat."

The researchers enrolled 60 men and women, between ages 30 and 65, who weighed an average of 215 pounds when the study began. Half went on a low-carb diet while the rest followed a low-fat diet; participants in both groups consumed the same number of calories. All met regularly with dietitians and attended an exercise program three times a week.

"This study shows that weight loss on a low-carb diet does not seem to affect cardiovascular risk," says Rachel Johnson, professor of both medicine and nutrition at the University of Vermont and co-chair of the American Heart Association's Nutrition Committee, who was not involved in the research. "The trial lasted only six months, however, and Johnson notes that eventual weight gain is a concern. So if you're serious about losing weight, the most important thing is to find a diet you can live with over the long term."

The research was presented at the American Heart Association scientific meeting in San Diego in March.

Also of interest: Eat for a healthy heart.

Nissa Simon, a health writer, lives in New Haven, Conn.