Effect of a high-carbohydrate diet intake on muscle glycogen repletion after exercise in rats previously fed a high-fat diet

Summary The effect of a high-carbohydrate (C) diet intake on muscle glycogen repletion during the early period of recovery from exercise was studied in rats previously fed a high-fat (F) diet. In experiment 1, 3 weekold male and in experiment 2, 3 week-old female rats were used. Rats were fed either the F or the C diet for 2–10 weeks ad libitum and then were meal-fed regularly twice a day for 25 days in experiment 1, or for 5 weeks in experiment 2. During the period of regular feeding, half of the rats in both dietary groups continued to eat as before (F-F and C-C) but the other half of the rats were switched to the counterpart diets (F-C and C-F) in experiment 1. In experiment 2, half of the F-F group were switched to the C diet (F-C) for 3, 7, and 14 days after the period of regular feeding. Pre-exercise glycogen content in soleus, red gastrocnemius, and heart muscles and liver was higher in rats fed the C diet (C-C and F-C) than in rats fed the F diet (F-F and C-F) in experiment 1. Glycogen repletion in red muscle 2 h after the ingestion of a glucose and citrate (3.0 and 0.5 g, respectively, per kg body mass) drink was also higher in the former than in the latter. There was a positive relationship in skeletal muscles between pre-exercise glycogen content and the rate of glycogen repletion. Compared with the rats maintained on the F diet (F-F), the rats switched to the C diet (F-C) for 3 and 7 days showed faster glycogen repletion in soleus and/or red gastrocnemius muscles in experiment 2. These results indicated that the poor capacity of restoration of skeletal muscle glycogen in rats previously fed the F diet was improved by the short-term dietary switch to the C diet.