EFFECT OF COINGESTION OF FAT AND PROTEIN WITH CARBOHYDRATE FEEDINGS ON MUSCLE GLYCOGEN-STORAGE

Dietary guidelines for achieving optimal muscle glycogen storage after prolonged exercise have been given in terms of absolute carbohydrate (CHO) intake (8-10 g . kg(-1) . day(-1)). However, it is of further interest to determine whether the addition of fat and protein to carbohydrate feedings affects muscle glycogen storage. Eight well-trained triathletes [23.1 +/- 2.0 (SE) yr; 74.0 +/- 3.4 kg; peak O-2 consumption = 4.7 +/- 0.4 l/min] undertook an exercise trial (2 h at 75% peak O-2 consumption, followed by four 30-s sprints) on three occasions, each 1 wk apart. For 24 h after each trial, the subjects rested and were assigned to the following diets in randomized order: control (C) diet(high glycemic index CHO foods; CHO = 7 g . kg(-1) . day(-1)), added fat and protein (FP) diet (C diet + 1.6 g . kg(-1) . day(-1) fat + 1.2 g . kg(-1) . day(-1) protein), and matched-energy diet [C diet + 4.8 g . kg(-1) . day(-1) additional CHO (Polycose) to match the additional energy in the FP diet]. Meals were eaten at t = 0, 4, 8, and 21 h of recovery. The total postprandial incremental plasma glucose area was significantly reduced after the FP diet (P < 0.05). Serum free fatty acid and plasma triglyceride responses were significantly elevated during the FP trial (P < 0.05). There were no differences between trials in muscle glycogen storage over 24 h (C, 85.8 +/- 2.7 mmol/kg wet wt; FP, 80.5 +/- 8.2 mmol/kg wet wt; matched-energy, 87.9 +/- 7.0 mmol/kg wet wt). Results of this study suggest that the addition of fat and protein to a recovery diet does not alter glycogen storage over 24 h, provided CHO intake is adequate.