Defining the functional properties of dietary protein and protein-rich foods in human energy expenditure
Food has a number of functional properties that can support the balance between energy intake and energy expenditure and, theoretically, one of these is the thermic effect of food. Including high-protein foods in meals may be advantageous in contributing to energy expenditure but, in practice, the evidence needs to relate to specific foods and normal dietary conditions. Using the human whole room calorimeter facility, we conducted three studies to examine the effects of: (i) higher and lower levels of protein on energy expenditure; (ii) high-protein meals using different foods to deliver the protein; and (iii) omnivorous and vegetarian cuisines in meal tests before and after a period of dietary intervention for weight loss. The meal effect of protein does not appear to differ between foods, and while high-protein diets might support weight loss, it may be difficult to prove a metabolic cause in the free-living environment.