Muscle glycogen storage after prolonged exercise: effect of the frequency of carbohydrate feedings

We reported previously that intake of carbohydrate foods with a high glycemic index (GI) produced greater glycogen storage and greater postprandial glucose and insulin responses during 24 h of postexercise recovery than did intake of low-GI carbohydrate foods. In the present study we examined the importance of the greater incremental glucose and insulin concentrations on glycogen repletion by comparing intake of large carbohydrate meals ('gorging') with a pattern of frequent, small, carbohydrate snacks ('nibbling'), which simulates the flattened glucose and insulin responses after low-GI carbohydrate meals. Eight well-trained triathletes (x̄ ± SEM: 25.6 ± 1.5 y of age, weighing 70.2 ± 1.9 kg, and with a maximal oxygen uptake (V̇O2 max) of 4.2 ± 0.2 L/min] undertook an exercise trial (2 h at 75% VO2 max followed by four 30-s sprints) to deplete muscle glycogen on two occasions, 1 wk apart. For 24 h after each trial, subjects rested and consumed the same diet composed exclusively of high GI carbohydrate foods, providing 10 g carbohydrate/kg body mass. The 'gorging' trial provided the food as four large meals of equal carbohydrate content eaten at 0, 4, 8, and 20 h of recovery, whereas in the 'nibbling' trial each of the meals was divided into four snacks and fed at hourly intervals (0-11, 20-23 h). However, there was no significant difference in muscle glycogen storage between the two groups over the 24 h (gorging: 74.1 ± 8.0 mmol/kg wet wt; nibbling: 94.5 ± 14.6 mmol/kg wet wt). The results of this study suggest that there is no difference in postexercise glycogen storage over 24 h when a high-carbohydrate diet is fed as small frequent snacks or as large meals, and that a mechanism other than lowered blood glucose and insulin concentrations needs to be sought to explain the reduced rate of glycogen storage after consumption of low-GI carbohydrate foods.