To determine relationships among dietary carbohydrate, aerobic exercise training, the thermic effect of food (TEF), and hormonal responses to feeding, 8 trained and 7 sedentary men consumed diets providing 15, 45, or 75% of energy as carbohydrate for 5 days. On Day 6, metabolic rate was measured before as well as 30, 60, 90, and 120 min after an 868-kcal liquid iesi breakfast. Blood was sampled hourly during Day 5 and during each metabolic rate measurement. The trained group had a larger TEF (40 ±2.4 vs. 31 ±3.0 kcal/2 hrs), greater insulin sensitivity, and greater plasma prolactin and corlisol levels, As carbohydrate in the treatment diet increased, carbohydrate utilization and thyroid stimulating hormone were higher and thyroxine was lower, but TEF was not significantly different. After the test meal, trained individuals had a higher TEF but the carbohydrate content of the treatment diet did not influence TEF.