Abstracts

Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating

The role of diet composition in response to overeating and energy dissipation in humans is unclear. The authors of this paper evaluated the effects of overconsumption of low-, normal-, and high-protein diets on weight gain, energy expenditure, and body composition.

Researchers used a single-blind, randomised controlled trial of 25 American healthy, weight-stable male and female volunteers, aged 18 - 35 years, with a body mass index between 19 and 30. The first participant was admitted to the inpatient metabolic unit in June 2005 and the last in October 2007.

After consuming a weight-stabilising diet for 13 - 25 days, participants were randomised to diets containing 5% of energy from protein (low protein), 15% (normal protein), or 25% (high protein), which they were overfed during the last 8 weeks of their 10 - 12-week stay in the inpatient metabolic unit. Compared with energy intake during the weight stabilisation period, the protein diets provided approximately 40% more energy intake, which corresponds to 954 kcal/d (95% CI, 884 - 1 022 kcal/d).

Body composition was measured by dual-energy X-ray absorptiometry bi-weekly, resting energy expenditure was measured weekly by ventilated hood, and total energy expenditure by doubly labelled water prior to the overeating and weight stabilisation periods and at weeks 7 - 8.

Overeating produced significantly less weight gain in the low-protein diet group (3.16 kg; 95% CI, 1.88 - 4.44 kg) compared with the normal-protein diet group (6.05 kg; 95% CI, 4.84 - 7.26 kg) or the high-protein diet group (6.51 kg; 95% CI, 5.23 - 7.79 kg) (p=0.002). Body fat increased similarly in all 3 protein diet groups and represented 50% to more than 90% of the excess stored calories. Resting energy expenditure, total energy expenditure, and body protein did not increase during overfeeding with the low-protein diet. In contrast, resting energy expenditure (normal-protein diet: 160 kcal/d (95% CI, 102 - 218 kcal/d); high-protein diet: 227 kcal/d (95% CI, 165 - 289 kcal/d)) and body protein (lean body mass) (normal protein diet: 2.87 kg (95% CI, 2.11 - 3.62 kg); high-protein diet: 3.18 kg (95% CI, 2.37 - 3.98 kg)) increased significantly with the normal- and high-protein diets.

Among persons living in a controlled setting, calories alone account for the increase in fat; protein affected energy expenditure and storage of lean body mass, but not body fat storage.

Bray GA, et al. JAMA 2012;307(1):47-55. doi: 10.1001/jama.2011.1918.