The Effect of the Timing of Meal Intake on Energy Metabolism during Moderate Exercise

Abstract

During exercise, the energy consumed in muscle tissue is mainly supplied by carbohydrates (CHO) and fats. In regard to health promotion and athletic sports, it is important to regulate the metabolism of these two substrates. Fats are supplied by meals, and also by adipose tissues, but CHO must be acquired from meals before exercise because little is stored as glycogen in the liver or muscle tissue. Previous studies have been conducted on the ergogenic effects of CHO feeding before exercise (1-10). It was reported that CHO solution (such as glucose and maltodextrin) feeding before exercise can improve exercise performance through enhanced endurance exercise capacity (2,4,5,10). Moreover, it was also reported that CHO mixed meal feeding before exercise can improve endurance exercise capacity (7,9,11).The intake of CHO elevates the secretion of insulin from the pancreas into the blood. Glucose and insulin in plasma reach a peak approximately 30 min after the ingestion of CHO and thereafter gradually decrease to the basal level. Insulin facilitates glucose uptake into skeletal muscle cells via the translocation of glucose transporter 4 (GLUT4) and then increases CHO oxidation. On the other hand, insulin prevents fat oxidation in muscle tissue by inhibition of lipoprotein lipase activity (12). Hyperinsulinemia tends to supply energy with a predominance of CHO over fats as the energy source in the initial period during exercise (7). Previous studies have shown, by examining timing of carbohydrate intake before exercise, that a shorter time from intake to exercise increases blood glucose and insulin levels at the start of exercise and these factors gradually decrease after the start of exercise (9, 10). Moreover, Chryssanthopoulos et al. (5) have reported that glucose intake at 30 min before exercise causes a rapid reduction of blood glucose after the beginning of exercise. On the other hand, Coyle et al. (13) have shown that carbohydrate utilization during exercise is higher under the condition of meal intake at 4 h before exercise compared with the fasting condition. Therefore, regardless of the timing of carbohydrate intake, it is likely that carbohydrate intake before exercise promotes its utilization as a major energy Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Hangi-cho, Shimogamo, Sakyo-ku, Kyoto, Kyoto 606-8522, Japan (Received June 5, 2013) Summary 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 performe...

Exercising Tactically for Taming Postmeal Glucose Surges

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The effect of meal frequency on biochemical cardiometabolic factors: A systematic review and meta-analysis of randomized controlled trials

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Pre-Exercise Carbohydrate Administration: Effect of Timing on the Rate of Glycogen Metabolism During Submaximal Running

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