FAT ADAPTATION WITH CARBOHYDRATE RECOVERY PROMOTES METABOLIC ADAPTATIONS DURING PROLONGED CYCLING

Abstract

297 For five days 8 trained cyclists (VO2peak 64.6 ±1.8 ml.kg−1.min) consumed either a high-carbohydrate (CHO) diet (9.6 g CHO.kg−1.d, 0.7 g fat.kg−1.d) or an isoenergetic high-fat (FAT) diet (2.4 g CHO.kg−1.d, 4.0 g carbohydrate.kg−1.d) while undertaking supervised daily training. On day 6, a high-CHO diet and rest were undertaken to restore muscle [glycogen] prior to performance testing on day 7. Adaptation to a FAT diet reduced RER during cycling at 70% of VO2peak; this was partially restored by 1 d of high-CHO (0.90 ±0.01, 0.82 ±0.01*, 0.87 ±0.01* for baseline, day 6 and day 7 respectively, *P<0.05). Corresponding RER values after the high-CHO diet were 0.91 ±0.01, 0.88 ±0.01* and 0.93 ±0.01*. On day 7, total fat oxidation was increased (94 ±6 vs. 61 ±5 g*) while carbohydrate oxidation was decreased (346 ±14 vs. 270 ±16 g*) throughout 2 hr of cycling at 70% VO2peak for FAT vs. CHO. Plasma [glucose] was better maintained throughout the 2 hr cycling after the FAT compared to the CHO diet. Performance of a subsequent time-trial (7 kJ.kg−1) was 30.73 ±1.12 vs. 34.17 ±2.48 min for FAT and CHO, mean improvement 8%, 95% CI −5.5% to 21%). These data show significant metabolic adaptations occur with a brief (5 d) period of FAT diet followed by CHO recovery. Although not statistically significant, the potential for performance enhancement could be meaningful to competitive cyclists undertaking a similar exercise challenge (2-3 hr cycling without CHO intake during the event).