Nutrition: Low-Protein Diet May Cost Lean Body Mass
By NICHOLAS BAKALAR

People consuming excess calories on a low-protein diet may gain less weight than others, a new study reports, but they do so at a cost: the loss of lean body mass.

In a controlled experiment published in the Jan. 4 issue of The Journal of the American Medical Association, researchers hospitalized 25 volunteers and put them on a weight-stabilizing diet for two to three weeks. Then they randomly assigned them to a diet composed of 5 percent, 15 percent or 25 percent protein, stuffing them for two months with 40 percent more calories than the weight-stabilizing diet had required.

Unsurprisingly, everyone put on weight. Those on the normal and high-protein diets gained an average of more than 13.5 pounds, and those in the low-protein group about seven pounds.

Everyone gained about 7.5 pounds of fat mass, but the results for lean body mass were different. The medium-protein group gained 6.3 pounds of lean body mass, and the high-protein consumers gained seven pounds. The low-protein eaters, on the other hand, lost 1.5 pounds of lean body mass.

“On a low-protein diet, the body has to get protein from somewhere, and it gets it from lean body mass,” said Dr. George A. Bray, the lead author and a professor of medicine at Louisiana State University. “You’re losing lean body mass, and there’s nothing to recommend that.”