Effects of acute treadmill exercise and delayed access to food on food selection in rats

Total energy intake and macronutrient self-selection were examined in rats following forced exercise (2 h treadmill, 15 m/min) or after a similar period of food deprivation without exercise. Acute exercise was realized at the end of the daytime. Return to the home cage for food access after exercise or after the same period of fasting was delayed for 0, 30, and 90 min. It has been shown that rats decreased body weight after all exercise situations. Food intake after deprivation was decreased in the first 3 h but was not modified over 24 h. The 24-h energy intake after exercise was identically reduced in the three situations. Carbohydrate and protein intakes were significantly reduced just after exercise. Protein decrease persisted all through the night and, to a lesser extent, during the following nycthemere. Fat decrease appeared later and was significant in the last part of the night. Increasing the delay to food access after exercise did not modify the total energy intake, but it significantly reduced carbohydrate intake. Those results show that exercise has a longer influence on food intake and, specifically, on macronutrient selection, than just food deprivation. Various hypotheses regarding central (cerebral neurotransmitters) and peripheral factors could be evoked in order to explain these modifications in the self-selected diet after an acute exercise.