Macro partitioning
Low muscle glycogen availability shifts fuel utilization towards increased lipid oxidation and reduced carbohydrate oxidation during exercise.
If you want to maximize fat oxidation during exercise, starting with low muscle glycogen (e.g., fasted or after a low-CHO meal) will shift your body to burn more fat. However, this comes at the cost of reduced carbohydrate oxidation and potentially lower performance intensity.
The shift towards fat oxidation when pre-exercise muscle glycogen is low is likely mediated by a number of contributing factors.
Why this rating
Supported by multiple studies cited (e.g., Arkinstall et al. [47], Coyle et al. [55]) showing consistent shifts in substrate utilization.
Source
Regulation of Muscle Glycogen Metabolism during Exercise: Implications for Endurance Performance and Training Adaptations
Mark A. Hearris et al. · Nutrients · 2018
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