OpenLB
Open Library of Bioscience

Although the intake of carbohydrates is important for the supplementation of energy substrate utilized during exercise, fat oxidation is possibly prevented by an elevation of insulin, and whether or not the timing of the intake of meals affects energy metabolism during exercise has not been clarified. The purpose of this study was to investigate the effect of the timing of the intake of meals taken at different times before exercise on the carbohydrate and fat metabolism during aerobic exercise. The subjects were eight young trained athletes who performed cycling exercise at the lactate threshold (LT) intensity for 60 min. They performed under five conditions consisting of a no-meal (water) trial, and four meal trials that had a normal meal at 1, 2, 3, and 4 h before the exercise. There were no significant changes for any trial in respiratory exchange ratio, or carbohydrate or fat oxidation rates during exercise. The serum insulin level before exercise in the meal trials was more elevated, the shorter the time to the start of the exercise from meal intake. A tendency for higher blood glucose was shown during exercise with a shorter interval time in the meal trials. No alterations were demonstrated for the serum free fatty acids in any of the groups. These results showed that the timing of the pre-exercise meal taken within a 4-h period before exercise did not affect the energy metabolism of the trained subjects during exercise at LT intensity.