Effect of Caloric Restriction and Protein Intake on Metabolism and Anabolic Sensitivity

1. Preliminary testing Prior to the study start, participants will be weighed and body composition will be determined using calipermetry (7 sites) and bioelectrical impedance. Peak oxygen uptake (VO2peak) will be assessed using an incremental exercise test on a bicycle ergometer. 2. Randomization Participants will proceed through each of the following conditions lasting 5 days: CR-LP: Participants will be restricted to 30 kcal/kg FFM/day and protein intake will be low (0.8 g/kg BW/day). CR-HP: Participants will be restricted to 30 kcal/kg FFM/day and protein intake will be high (1.7 g/kg BW/day). CON: Participants will be in energy balance and consume 1.7 g protein/kg BW/day. 3. Diet Prescription Dietary energy intake will be controlled using clinical products and maltodextrin to meet target energy intakes. Participants will received calcium and Vitamin D supplementation throughout the study. 4. Exercise Prescription During all conditions, participants will conduct daily supervised exercise on a bicycle ergometer at an exercise intensity of 60% VO2peak. Exercise duration will be adjusted individually such that exercise energy expenditure will amount to 15 kcal/kg FFM/day. Additional exercise and intense physical activity will be prohibited. 5. Assessments The following assessments will be conducted prior to the start of each condition as well as upon completion of each condition: body weight and composition (impedance), fasting blood draw for assessment of metabolic and anabolic hormones, resting metabolic rate, aerobic fitness (VO2peak), and questionnaires. 6. Washout Once a participant has completed a study condition, participant will be allowed a washout of at least 14 days to allow protein balance to return to baseline (Hoffer \& Forse, 1990). During this time, participants will resume their regular diet and physical activity.