January 9, 2012

Protein vs. Calories for Weight Loss

(Ivanhoe Newswire) — As the world enters into the year 2012 many people are bringing additional body weight into the New Year; and with it a New Year´s resolution almost as old as the world itself — to lose weight. Obesity is steadily on the rise in the United States, with more than 60 percent of U.S. adults overweight and more than 30 percent categorized as being obese. Adults are constantly searching for new means to shed those unwanted pounds, but a new study, suggests that protein may be your best bet.

George A. Bray, M.D., of the Pennington Biomedical Research Center, Baton Rouge, LA., and his colleagues conducted a study to determine whether the level of dietary protein differentially affected body composition, weight gain, or energy expenditure under tightly controlled conditions. The trial was conducted among 25 healthy male and female volunteers with a stable weight. The participants ranged in age from 18 to 35 with a body mass index between 19 and 30.

Volunteers participated in three protein diet groups: low, normal, and high. The first participant was admitted to the impatient metabolic unit in June 2005 and the last October 2007. After consuming a weight-stabilizing diet for 13 to 25 days, volunteers were randomized to receive diets containing five percent of energy from protein (low protein), 15 percent (normal protein), or 25 percent (high protein), which they were overfed during the last 8 weeks of their 10 to 12 week stay in the inpatient metabolic unit. During the overeating period participants´ lean body mass (body protein) decreased by 1.5 lbs. (0.70 kg) in the low protein diet group compared with a gain of 6.3 lbs. (2.87 kg) in the normal protein diet group and 7 lbs. (3.18 kg) in the high protein diet group.

Bray and his colleagues discovered that, "Body fat increased similarly in all three protein diet groups and represented 50 percent to more than 90 percent of the excess stored calories." Compared with energy intake during the weight stabilization period, the protein diets provided approximately 40 percent more energy intake, which corresponds to 954 calories a day.

Bray and his colleagues found that, "resting energy expenditure, total energy expenditure, and body protein did not increase during overfeeding with the low protein diet."

The study also showed that all participants, regardless of gender, gained weight. The weight gain in the low protein diet group was significantly less than in the other two groups (6.97 lbs. [3.16 kg], vs. 13.3 lbs. [6.05 kg] for the normal protein diet group and 14.4 lbs. [6.51 kg] in the high protein diet group.

The researchers concluded, that "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 calories. Calories alone, however, contributed to the increase in body fat. In contrast, protein contributed to the changes in energy expenditure and lean body mass, but not to the increase in body fat. Researchers found that "calories are more important than protein while consuming excess amounts of energy with respect to increases in body fat."

SOUCE: JAMA, January 2012