Exercise intensity and the thermic effect of food.

This study investigated the effect of varying exercise intensity on the thermic effect of food (TEF). Sixteen lean male subjects were matched for VO2 max and randomly assigned to either a high or low intensity group for 30 min of treadmill exercise. Caloric expenditure was measured using indirect calorimetry at rest and at 30-min intervals over 3 hrs following each of three conditions: a 750-kcal liquid meal, high or low intensity exercise, and a 750-kcal liquid meal followed by high or low intensity exercise. Low intensity exercise enhanced the TEF during recovery at 60 and 90 min while high intensity enhanced it only at 180 min but depressed it at 30 min. Total metabolic expense for a 3-hr postmeal period was not differently affected by the two exercise intensities. Exercise following a meal had a synergistic effect on metabolism; however, this effect was delayed until 180 min postmeal when exercise intensity was high. The circulatory demands of high intensity exercise may have initially blunted the TEF, but ultimately the TEF measured over the 3-hr period was at least equal to that experienced following low intensity exercise.