Meal-induced thermogenesis following exercise training in the rat

The effects of treadmill exercise on the thermic effect of a meal were studied in male Sprague-Dawley rats (370 to 400 g, 4 to 5 months of age). Rats were exercised for 60 min, 5 d·wk^-1 for 8 to 10 wk, at a speed of 27 m·min^-1 and with a grade of 8%. Sedentary (N=9) and exercised (N=8) rats were given food and water ad libitum. Oxygen consumption was measured at rest and following the ingestion of a meal consisting of 81% carbohydrate, 9% protein, and 10% fat (by calories). In those animals that were exercised, oxygen consumption measurements were performed 24 h after the completion of an exercise bout. Although all animals gained weight during the experimental period, the exercised group gained significantly less than did the sedentary rats. Resting oxygen consumption [ml/(min x g bodymass^.67)] was not significantly different between the exercised and sedentary rats. The ingestion of the high carbohydrate meal significantly increased mass-independent oxygen consumption above resting values in both groups; the values for the exercised rats were greater than those for the sedentary rats. However, there were no differences between the exercised and sedentary rats in meal-induced oxygen consumption when the data were expressed as a function of lean body mass [ml/(min x g lean body mass)] or as mass-independent lean body mass [ml/(min x g lean body mass^.67)]. These data suggest that exercise-trained rats have increased diet-induced thermogenesis and may be one factor in the loss of weight sometimes found in response to exercise.