The Impact of a High Protein Diet on Substrate Oxidation and Energy Metabolism

The aim of this study is to investigate the impact of a high protein diet (achieved through the use of a high protein supplement) versus standard diet on substrate oxidation and energy expenditure using a state-of-the-art live-in whole body calorimetry unit (WBCU). This study will be an acute randomized, controlled, cross-over trial. Healthy women (n=24) will receive a run-in diet for three days and will then be randomly allocated into one of the following groups: 1) Control group receiving an eucaloric standard diet (55% of carbohydrate, 15% of protein, and 30% of lipid); 2) High-protein group: eucaloric high protein diet (35% of carbohydrate, 40% of protein, and 25% of fat) constructed around a soy protein-based meal replacement. The wash-out period will be of approximately one month. While receiving the diets in the WBCU for 32 hours, participants' overall change in energy metabolism including respiratory quotient will be assessed. Additional assessments include metabolic blood markers (glucose, insulin, lipid panel, peptide tyrosine-tyrosine, ghrelin, leptin, free glycerol, and free fatty acids), and appetite sensations (hunger and satiety). Body composition and energy requirements will be assessed at baseline using dual-energy X-ray absorptiometry and indirect calorimetry, respectively. It is expected that the high-protein diet will increase lipid oxidation, and energy expenditure, with other favorable changes in the additional markers when compared to the control group.