Diets that trim belly fat improve blood flow

JOHNS HOPKINS (US) — Overweight people who shed belly fat improve their blood vessel health whether they use a low-carb or a low-fat diet, researchers say.

The more belly fat you lose, the better your arteries are able to expand when needed, allowing more blood to flow more freely, the researchers report.

“Our study demonstrated that the amount of improvement in the vessels was directly linked to how much central, or belly fat, the individuals lost, regardless of which diet they were on,” says lead investigator Kerry J. Stewart, a professor of medicine at  Johns Hopkins University and director of clinical and research exercise physiology at the Heart and Vascular Institute.

“This is important,” Stewart says, “since there have been concerns that a low-carb diet, which means eating more fat, may have a harmful effect on cardiovascular health. These results showed no harmful effects from the low-carb diet.”

Being overweight increases the risk of cardiovascular disease, especially if fat is accumulated in the belly above the waist. Low-carbohydrate diets, including the Atkins and South Beach diets among others, restrict intake of foods like pasta or bread in favor of food with higher protein or fat content. A low-fat diet, on the other hand, hold down calorie intake by restricting fats, especially saturated fat and cholesterol.

Stewart and his colleagues presented their findings March 13 at an American Heart Association meeting in San Diego on cardiovascular disease prevention. They said they studied 60 men and women who weighed an average of 215 pounds at the start of the program. Half went on a low-carb diet while the others followed a low-fat diet. All took part in moderate exercise and their diets provided a similar amount of calories each day.

In the six-month study, participants on a low-carbohydrate diet lost an average of 28.9 pounds, about 10 pounds more, on average, than the 18.7 pounds dropped by those following a low-fat diet.

In order to evaluate the health of the participants’ blood vessels before and after weight loss, the researchers constricted circulation in the upper arm for five minutes with a blood pressure cuff. In this test, when the cuff is released, a healthier artery will expand more, allowing more blood to flow through the artery.

The researchers measured how much blood reached the fingertips before, during and after constriction of the artery. Stewart says this test indicates the overall health of the vascular system throughout the body. The researchers found that the more belly fat a person had lost, the greater the blood flow to the finger, signaling better the function of the artery.

In the low-carb diet used in the study, up to 30 percent of calories came from carbohydrate sources such as bread, pasta and certain fruits, while 40 percent was from fat consumed from meat, dairy products and nuts. In contrast, the low-fat diet consisted of no more than 30 percent of calories from fat and 55 percent from carbs.

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