(PTFS20-01-24) Metabolic Responses to Pre-exercise High and Low Glycemic Meals: A Controlled Crossover Trial

Objectives: Guidelines on the quantity of CHO intake before exercise have been well defined but the quality of CHO is yet to be explored to give recommendations on pre-exercise nutrition to the exercisers.

Methods: The crossover trial included 10 participants(28 ± 1.5 years).Test food was one serving of low GI sports bar(GI:39)(LGI) which was optimized using RSM and reference food was glucose powder(45g available carbohydrates)(HGI) and was served after 12 hours of fasting. Two exercise trials (1 min of jogging-6kmph and then 14 mins of running-9kmph which is followed by 1-2 mins for a blood test) were conducted for 45 mins on a motorized treadmill after one hour of ingestion of meals with a washout period of 2 days. Blood was sampled after 1hr ingestion of meals(pre-exercise),15,30 and 45 mins of exercise.

Results: A Mann-Whitney U test indicated that pre-exercise blood insulin levels were significantly lower after 1hr of ingestion of LGI(1.78 ± 0.11U/l) compared with HGI(6.1 ± 0.16). The decrease in insulin till 45th min of the exercise was gradual after consumption of LGI(0.73 ± 0.13) and steep after HGI(0.72 ± 0.10) using post-hoc test. The pre-exercise blood glucose levels were significantly lower post 1hr of ingestion of LGI (87 ± 3.2mmol/L) compared with HGI(134.7 ± 3.6). There was a transient dip in the blood glucose till 15^th min and 30^th min during exercise after ingestion of LGI and HGI meals, respectively. The pre-exercise blood TG levels were significantly lower post 1hr of LGI consumption(68.8 ± 3.19mg/dl) compared with HGI(95.5 ± 6.24). After ingestion of LGI, the blood TG increased till 30^th min(88.3 ± 3.56) during exercise then decreased, while it decreased gradually after consumption of HGI till 30^th min(82.5 ± 5.91) during exercise and then increased. The pre-exercise blood lactate levels after one hour of ingestion of meals were the same (1.13 ± 0.05mmol/L). The blood lactate increased till 30^th min(3.43 ± 0.09) during exercise after ingestion of LGI and then decreased while it gradually increased till 45^th min(3.41 ± 0.12) after ingestion of HGI.

Conclusions: Sustained blood glucose levels were seen during exercise after the ingestion of LGI than HGI. Blood TG increased during exercise after ingestion of LGI meal because lipolysis was enhanced due to a rise in catecholamines and a decrease in insulin which also increased blood lactate till 30^th min resulting in a decrease in fat oxidation by 45^th min of exercise.

Funding Sources: N/A