Exercise-Induced Metabolic Compensation; a Physiological Adaptive Response to Exercise Training

The primary aim of this proposal is to identify changes in the volume of highly metabolic organs (liver, kidneys, and brain) that occur as a physiological adaptation to exercise training and lower the resting energy expenditure. Secondary aims are to identify changes in the metabolic efficiency of muscle in low levels of physical activity and evaluate the effects on components of total daily energy expenditure including the sleeping metabolic rate (SMR) and diet induced thermogenesis (DIT).

Using a clinical trial type protocol, 16 overweight (body mass index: 25-30 kg/m2) men (n=8) and women (n=8) aged 21 to 45 years will exercise for 3 months in a moderate intensity regimen of 20 kcal/week/kg body weight that reflects current recommendations for weight management. The volume of various organs will be measured pre- and post-exercise intervention using magnetic resonance imaging (MRI). A cycling ergometer with a varied workload will be used to assess muscle metabolic efficiency. Changes in overnight SMR and 4 hours post breakfast DIT will be evaluated by whole human room indirect calorimetry ("metabolic chamber"). In addition, free-living Total Energy Expenditure (TEE) will be measured for ten days pre- and post-intervention by doubly labeled water.