Carbohydrate, lipid and amino acid metabolism following physical exercise in man.

To elucidate early metabolic adaptations of physical training obese and nonobese subjects were studied before and at different intervals after 1 h of bicycle exercise at 70% of maximal working capacity. Four h after exercise intravenous glucose tolerance (IVGT) and plasma level of alanine were decreased. Compared to the diurnal variation plasma concentration of cortisol was increased. Twenty-four hours after exercise plasma concentrations of cortisol and trihlycerides were decreased. Furthermore, plasma insulin during IVGT test was decreased and blood glycerol increased in the obese subjects. There were no changes in basal insulin, IVGT, or plasma levels of amino acids which were elevated in the obese subjects (valine, isoleucine, leucine, tyrosine, phenylalanine). Forty-eight hours after exercise plasma insulin during IVGT test and plasma triglycerides remained decreased in the obese subjects. Low cortisol levels 24 h after exercise might result in increased insulin effect leading to low plasma insulin levels seen in physically trained subjects. Elevated glycerol levels in the obese subjects might be the first sign of diminishing fat stores secondary to increased lipolysis.