Effect of a high carbohydrate pre-exercise meal on metabolic and performance-related parameters in male athletes following two different strategies to improve fat utilization: An exploratory examination

The purpose of this additional examination of a larger intervention was to determine the effects of a carbohydrate-rich pre-exercise meal on metabolic and performance-related parameters in a group of male endurance athletes, who had previously followed either a high fat low carbohydrate (HFLC; n = 6) or high carbohydrate low glycaemic (LGI; n = 6) diet for 4 weeks. Participants continued their regular training routine during the intervention. Respiratory exchange ratio (RER), lactate concentrations ([La−]), substrate oxidation rates at rest and during a cycle ergometry with incremental workload were determined in the fasted state and 2 h after consuming a carbohydrate-rich (2 g per kg of body mass) pre-exercise meal. Power output at lactate thresholds, peak oxygen uptake (V̇O2peak), absolute and relative peak power during the incremental test were assessed. After consuming the pre-exercise meal, both groups showed increased levels of RER, [La−] and carbohydrate oxidation at rest and during the incremental test (p  0.8), and an improved V̇O2peak (p  0.5). Rm ANOVA revealed significant group differences in metabolic parameters. Despite meaningful baseline differences ([La−]: p = 0.133; ηp2 = 0.185; RER: p = 0.037; ηp2 = 0.367; carbohydrate oxidation: p = 0.041; ηp2 = 0.355) upregulation of carbohydrate metabolism was more pronounced in the LGI subgroup compared to the HFLC group after 4-weeks intervention, in both fasted ([La−]: p = 0.130; ηp2 = 0.214; RER: p = 0.001; ηp2 = 0.713; carbohydrate oxidation: p = 0.001; ηp2 =0.684) and postprandial states ([La−]: p = 0.036; ηp2 =0.369; RER: p = 0.001; ηp2 =0.705; carbohydrate oxidation: p = 0.001; ηp2 =0.665). Peak power during the final incremental test was slightly higher in the LGI subgroup compared with the HFLC subgroup (p = 0.320; ηp2 = 0.100). In this group of male endurance athletes, a LGI diet seemed to result in more favourable performance metrics as compared to a HFLC diet despite increases in carbohydrate availability before undertaking the performance test likely due to the ability to sustain higher workloads in training.