The effect of prior exercise on the thermic effect of carbohydrate versus fat feeding in man
Prior exercise potentiates the thermic effect of a carbohydrate meal. The purpose of this study was to determine if the potentiating effect of exercise is unique to carbohydrate meals or whether prior exercise also potentiates the thermic effect of a fat meal. Subjects were 15 healthy females (24 years, 60 KG, 20% body fat). Each subject completed an exercise and a control trial for each meal, each trial on a separate day. Meal size was 2510 KJ (600 kcal) and consisted of 100% carbohydrate, compared with 90% fat combined with 10% carbohydrate. Subjects exercised for 45 minutes at 70% of VO{dollar}\sb2{dollar} max on a cycle ergometer. Once VO{dollar}\sb2{dollar} had returned to baseline following exercise, subjects ingested a test meal. As a control, subjects ingested a test meal without prior exercise. The thermic effect of food (TEF) was determined by indirect calorimetry over a 2 hour period following meal ingestion. The thermic effect of the carbohydrate meal was 50% greater than that of the fat meal (p {dollar}<{dollar} 0.05). Thermic effect of food was increased by 59% over control when the carbohydrate meal was ingested after exercise (E = 124 {dollar}\pm{dollar} 19 vs C = 78 {dollar}\pm{dollar} 17 kJ/2hr, P {dollar}<{dollar} 0.01). However, TEF was not increased significantly over control with the fat meal after exercise (E = 75 {dollar}\pm{dollar} vs C = 61 {dollar}\pm{dollar} 10 kJ/2hr). These results suggest that the potentiation of the thermic effect of a meal by prior exercise depends on the composition of the meal, essentially excluding meals consisting primarily of fat.
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