Influence of low versus moderate glycemic index of diet on substrate oxidation and energy expenditure during incremental exercise in endurance athletes: a randomized counterbalanced cross-over trial

Abstract

The study was aimed at assessing the influence of 3-week low glycemic index (LGI) versus moderate glycemic index (MGI) diet on substrate oxidation during incremental exercise. 17 runners completed two 3-week trials of either LGI or MGI diet in a randomised counterbalanced manner. Before and after each trial the incremental cycling test was performed. Metabolic alternations were observed only within tested diets and no significant differences in fat and carbohydrate (CHO) oxidation were found between MGI and LGI diets. Following MGI diet CHO oxidation rate increased. The AUC of fat oxidation decreased after both diets. Percent contribution of fat to energy yield declined, whereas contribution of CHO was augmented following MGI diet. This study indicates that the 3-week MGI diet increased the rate of carbohydrate oxidation during incremental cycling test and improved performance in acute intense exercise test, while both high-carbohydrate diets downregulated fat oxidation rate.

Keywords:

• Endurance exercise
• exercise metabolism
• sports nutrition
• glycemic index
• carbohydrates
• runners

Acknowledgements

The authors thank the volunteering athletes for participating in the study. We gratefully acknowledge financial support for this work, provided by the departmental sources.

Disclosure statement

The authors report no conflicts of interest with this work.

Additional information

Funding

This work was funded by the internal sources of the Poznań University of Life Sciences.