Mixed
Five days of high-fat diet combined with endurance training, followed by one day of carbohydrate restoration, decreases pyruvate dehydrogenase (PDH) activation and muscle glycogenolysis during exercise, despite fully restoring muscle glycogen levels.
If you follow a high-fat diet while training, simply eating carbohydrates the day before an event will not immediately restore your body's ability to burn those carbohydrates efficiently. Your muscle enzymes (specifically PDH) remain suppressed, meaning you will continue to rely more on fat oxidation even with full glycogen stores. This suggests metabolic adaptations persist beyond substrate availability.
Results indicate that previously reported decreases in whole body CHO oxidation and increases in fat oxidation after the FAT-adapt protocol are a function of metabolic changes within skeletal muscle... Estimates of glycogenolysis during the 1st min of exercise at 70% V˙ O2 peak and the 1-min sprint were also lower after FAT-adapt
Why this rating
Randomized crossover design with well-trained subjects, though sample size is small (n=7) and some respiratory data was missing.
Source
Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration
Trent Stellingwerff et al. · American Journal of Physiology-Endocrinology and Metabolism · 2005
DOI 10.1152/ajpendo.00268.2005
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