However, a study of 25 healthy individuals living in a controlled setting who were randomized to overeat different levels of protein diets found protein did contribute to changes in energy expenditure and lean body mass.
"Obesity has become a major public health concern with more than 60 percent of U.S. adults categorized as overweight and more than 30 percent as obese," Dr. George A. Bray of the Pennington Biomedical Research Center in Baton Rouge, La., said in a statement.
Bray and colleagues conducted a randomized controlled trial of 25 healthy, weight-stable male and female volunteers, ages 18-35, with a body mass index between 19 and 30.
After consuming a weight-stabilizing diet for 13 to 25 days, participants were randomized to receive diets containing 5 percent of energy from protein (low protein), 15 percent (normal protein) or 25 percent (high protein) during the last eight weeks of their 10- to 12-week stay in the inpatient metabolic unit.
Compared with energy intake during the weight stabilization period, the researchers boosted those on the protein diets with about 954 calories a day.
The study, published in the Journal of the American Medical Association, found weight gain when eating a low protein diet was blunted compared with weight gain when eating a normal protein diet with the same number of extra calories.
However, calories alone, contributed to the increase in body fat, the study said.