Metabolic responses to a meal during rest and low-intensity exercise

The effects of intermittent exercise on increases in metabolic rate and plasma insulin, glucose, and triglyceride concentrations at 1, 2, and 3 h after an 800-kcal meal were examined in six healthy volunteers. Mean plasma insulin concentrations were significantly lower (-61%) at the end of a 15-min exercise session on a stationary bicycle (50 W) at 1 h after the meal, compared to insulin concentrations when subjects rested throughout the test, but had returned to normal resting levels by 30 min after the end of the exercise bout. Mean plasma glucose concentrations were not significantly different at the end of the exercise bouts than they were at comparable times of the resting study, but were about 20 mg/dl higher 30 min after the exercise bouts. Plasma triglyceride concentrations increased by approximately 50% after the meal, and this effect was not influenced by exercise. Resting metabolic rate increased by 19.9 +/- 2.1, 20.6 +/- 2.1, and 15.1 +/- 2.4 kcal/h at 1, 2, and 3 h after meal onset, and the metabolic rate during exercise increased by 13.8 +/- 4.4, 16.8 +/- 3.5, and 11.6 +/- 3.4 kcal/h at 1, 2, and 3 h after meal onset. These data suggest that postprandial exercise would be no more beneficial than preprandial exercise in increasing energy expenditure.