A low glycemic index meal before exercise improves endurance running capacity in men.

This study investigated the effects of ingesting a low (LGI) or high (HGI) glycemic index carbohydrate (CHO) meal 3 h prior to exercise on endurance running capacity. Eight male recreational runners undertook two trials (LGI or HGI) which were randomized and separated by 7 d. After an overnight fast (12 h) the subjects ingested either a LGI or HGI meal 3 h prior to running at 70% VO2max until exhaustion. The meals contained 2 g/kg body mass CHO and were isocaloric and iso-macronutrient with calculated GI values 77 and 37 for the HGI and LGI respectively. The run times for the LGI and HGI trials were 108.8 +/- 4.1 min and 101.4 +/- 5.2 min respectively (P = 0.038). Fat oxidation rates were higher during exercise after the LGI meal than after the HGI meal (P < 0.05). In summary, ingestion of a LGI meal 3 h before exercise resulted in a greater endurance capacity than after the ingestion of a HGI meal.