Calories For Fat, Protein For Lean Mass

Protein percentage in diet leads to different outcomes

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Eating too much - but not enough protein - might mean you'll weigh less than heavy protein eaters, but you'll likely be carrying around a higher percentage of fat.

A new study shows that what matters most in looking at where extra fat comes from, it's calories and not protein that makes the difference. And if you're carrying around extra weight, lean muscle is better than fat.

"Protein in your diet keeps your body fat % lower."

A controlled study led by George A. Bray, M.D., of the Pennington Biomedical Research Center, Baton Rouge, La. looked at three diets with varying amounts of protein to investigate how eating different amounts of protein affects a person's body composition, weight, and their energy expenditure, or how efficiently they burn calories.

They found that overeating leads to weight gain with all three diets, but those eating a higher percentage of protein gained more lean body mass rather than extra fat storage.

"if you're going to lose weight, it's better to lose fat," said registered and licensed dietitian Eve Pearson, talking with dailyRx. "People who have a balanced diet with lean protein will retain more lean body mass in their weight loss goal."

The study was conducted from June 2005 through October 2007 with 25 healthy men and women between the ages of 18 and 35 and whose BMI was between 19 and 30.

The participants first spent two to three weeks eating a specific diet in a metabolic clinic to ensure their weight remained stable.

They then spent another eight weeks in the clinic, where they were randomly assigned to a low, average or high protein diet that provided 40 percent more calories (954 extra calories) daily than the stabilizing diet.

The low protein diet consisted of 5 percent protein, the normal was 15 percent protein, and the high was 25 percent. The percentage of carbohydrates in all three diets was 41 or 42 percent, and the remaining percentages were fat.

While all participants gained weight, the high protein group gained the most,14.4 pounds on average, compared to 7 pounds in the low-protein group and 13.3 pounds in the normal protein group.

Body fat percentage, however, increased at the same rate in all three groups, so the extra pounds in the higher protein groups came more from an increase in lean body mass.

In the low protein group, 90 percent of the extra calories the participants ate went to fat storage, compared to only 50 percent of the extra calories turning into fat storage in those who ate the two higher protein diets.

The normal and high protein diet groups also showed an increase in the amount of calories they burned at rest.

The randomized controlled trial was funded in part by a U.S. Department of Agriculture grant and by Louisiana State University. The paper appears in the January 4 issue of JAMA.

Reviewed by: 
Review Date: 
January 6, 2012
Last Updated:
February 3, 2012