Study: High-Protein Diet Boosts Exercise Benefits

URBANA, Ill. -- Researchers have a new diet recommendation for women trying to lose weight.

A study published in the August issue of the Journal of Nutrition says a high-protein diet can make regular exercise more effective for women by helping to build muscle while trimming body fat.

"There's an additive, interactive effect when a protein-rich diet is combined with exercise," said lead researcher Donald Layman of the University of Illinois. "The two work together to correct body composition; dieters lose more weight, and they lose fat, not muscle."

The four-month study of 48 women involved dieting combined with exercise. Half the participants followed a protein-rich diet, and the other half ate a higher-carbohydrate, lower-protein diet based on the U.S. Department of Agriculture's food guide pyramid.

Layman said women on both diets lost weight, but the protein-rich regimen significantly reduced abdominal fat and the risk factors for heart disease. In comparison, the higher-carb, lower-protein diet reduced the effectiveness of exercise, Layman said in a news release.

"Both diets work because, when you restrict calories, you lose weight. But the people on the higher-protein diet lost more weight. Some people refer to this as the metabolic advantage of a protein-rich diet," said Layman.

The study was funded by the Illinois Council on Food and Agricultural Research, the National Cattlemen's Beef Association, the Beef Board and Kraft Foods.

Layman said he and his team think federal diet recommendations don't contain enough of the amino acid leucine, which is found in protein-rich foods.

"The average American diet contains 4 or 5 grams of leucine, but to get the metabolic effects we're seeing, you need 9 or 10 grams," he said.