Author Affiliation: Department of Human Biology, Maastricht University Medical Centre, Maastricht, the Netherlands (firstname.lastname@example.org).
To the Editor: When people overeat, diet composition should affect the amount of excess energy available for storage based on the difference in amount of adenosine triphosphate required for the initial steps of metabolism for each macronutrient. The intake of nutrients increases energy expenditure, in which the measured thermic effect is 0% to 3% for fat, 5% to 10% for carbohydrates, and 20% to 30% for proteins.1 The higher the protein content and the lower the fat content of a diet, the lower the net availability of energy for body functions including energy storage. Thus, it is surprising that Dr Bray and colleagues2 observed that protein content of the diet affected energy expenditure but not body fat storage. On the other hand, they stated that participants eating 40% more energy intake than required for weight stabilization stored 90% of the extra energy as fat when fed a low protein diet (containing 5% of energy from protein) and stored only about 50% of the excess energy as fat when fed a normal or high protein diet (containing 15% or 25% of energy from protein, respectively).
Westerterp KR. Dietary Protein and Weight Gain. JAMA. 2012;307(16):1691-1692. doi:10.1001/jama.2012.532