Methods for increasing endurance and fat metabolism in humans

A method of increasing endurance and fat metabolism in human beings, comprising:

• providing an oral nutritional supplement, comprising:
• 1-arginine hydrochloride;
• oxo-proline;
• 1-lysine hydrochloride;
• and
• n-acetyl-1-cysteine, 1-glutamine, or both;
• wherein the L-arginine hydrochloride is present in an amount from 0.1 to 6 mmol, the oxo-proline is present in an amount from 0.1 to 8 mmol, and the L-lysine hydrochloride is present in an amount from 0.1 to 12 mmol;
• and
• orally administering the nutritional supplement to a human being to increase endurance and fat metabolism.