Effects of Milk Proteins on Protein Synthesis in Healthy Male Subjects Fed a Hypercaloric, High Sucrose Diet

This study aims at assessing the hypothesis that dietary protein content is a major factor regulating lean body mass gain and energy expenditure during overfeeding, and thus long term body weight gain To test this hypothesis, healthy normal weight male and female subjects will before and after a 7-day hypercaloric, high-sucrose diet (+40% excess energy as sucrose) and either a low (5% total energy) or a high (20% total energy) protein intake. Each subject will be studied with both low- and high protein diets according to a randomized, crossover study. On each occasion the following measurements will be done in basal conditions (after 2-day isoenergetic, controled diet) and at the end of the 7-day overfeeding: * whole-body protein turnover, oxidation and synthesis in fasting conditions and fed conditions (13C-labelled leucine) * intrahepatic and intramuscular fat concentration (1H-Magnetic Resonance Spectroscopy) * Energy metabolism in fasted and fed conditions (indirect calorimetry) * plasma concentration of glucose, non-esterified fatty acids, total triglyceride, very-low density lipoprotein (VLDL)-triglyceride, insulin, glucagon, growth hormone (GH), insulin-like growth factor 1 (IGF1), insulin-like growth factor binding protein (IGFBP) 1,2 and 3 in fasting and fed conditions The effects of high-protein and low-protein sucrose overfeeding on whole body protein synthesis will be compared using two-way ANOVA; relationships between changes in whole body protein synthesis on one hand, and intrahepatic/intramuscular fat concentrations, total energy expenditure, and plasma concentration of metabolic variables on the other hand, will be evaluated by linear regression analysis