A modest reduction in consumption of carbohydrate foods may promote loss of deep belly fat, even with little or no change in weight, a new study finds.
When paired with weight loss, consumption of a moderately reduced carbohydrate diet can help achieve a reduction of total body fat, according to principal author Barbara Gower, PhD, a professor of nutrition sciences at the University of Alabama at Birmingham.
"These changes could help reduce the risk of developing Type 2 diabetes, stroke and coronary artery disease," Gower said, noting that excess visceral, or intra-abdominal, fat raises the risk of these diseases.
Gower and her colleagues conducted the study, with funding from the National Institutes of Health, in 69 overweight but healthy men and women. Subjects received food for two consecutive eight-week periods: first a weight maintenance intervention, and then a weight loss intervention, which cut the number of calories that each person ate by 1,000 each day.
Subjects received either a standard lower-fat diet or a diet with a modest reduction in carbohydrates, or "carbs," but slightly higher in fat than the standard diet. The moderately carb-restricted diet contained foods that had a relatively low glycemic index, a measure of the extent to which the food raises blood glucose levels. This diet consisted of 43 percent calories from carbohydrates and 39 percent calories from fat, whereas the standard diet contained 55 percent of calories from carbohydrates and 27 percent from fat. Protein made up the other 18 percent of each diet.
At the beginning and end of each study phase, the researchers measured the subjects' fat deep inside the abdomen and their total body fat using computed tomography (CT) and dual-energy x-ray absorptiometry (DXA) scans.
After the weight maintenance phase, subjects who consumed the moderately carb-restricted diet had 11 percent less deep abdominal fat than those who ate the standard diet. However, when the researchers analyzed results by race, they found it was exclusive to whites. Whites have more deep abdominal fat than Blacks even when matched for body weight or percent body fat, and may benefit from loss of this metabolically harmful depot, Gower said.
During the weight loss phase, subjects on both diets lost weight. However, the moderately carb-restricted diet promoted a 4 percent greater loss of total body fat, Gower said. "For individuals willing to go on a weight-loss diet, a modest reduction in carbohydrate-containing foods may help them preferentially lose fat, rather than lean tissue," she said. "The moderately reduced carbohydrate diet allows a variety of foods to meet personal preferences."