The fat burning ability of melatonin during submaximal exercise

ABSTRACT The regulation of the balance between glucose and lipid use during exercise has gained increasing attention in the last decades. The contribution of fat and glucose to energy expenditure can be modulated by hormones and other endogenous factors. The increase in melatonin during exercise may be linked to an enhancement in lipid utilization, reflected by an increase in triglyceride concentration. The purpose of this study was to explore the effect of daytime melatonin administration on plasma glucose, triglycerides, and cortisol responses to submaximal exercise. Eight physical education students were asked to run for 45 minutes at 60% of their maximum aerobic speed after 50 minutes of either melatonin-(6 mg) or placebo consumption. Cortisol, triglycerides, and glucose were measured in plasma samples before and immediately after exercise. Post-exercise cortisol, triglycerides, and glucose levels were corrected for fluid shifts. In both conditions , post-exercise cortisol significantly increased (by ≥20%) . Post-exercise glucose levels significantly increased only in the placebo condition . However, post-exercise triglyceride levels significantly increased only in the melatonin condition. To conclude, acute melatonin administration decreases the glucose response while increasing triglycerides’ response to exercise. Therefore, it would be possible to suggest that exogenous melatonin administration before endurance exercise could promote fat burning.