Macro partitioning
A high-fat, low-carbohydrate diet (high dietary fat intake) increases whole-body fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans, whereas low carbohydrate availability alone does not drive these adaptations.
If you are a trained endurance athlete, consuming a diet with >65% of calories from fat (while keeping carbs low at <20%) for about 5 days will significantly increase your body's ability to burn fat during exercise and reduce mitochondrial respiration rates. This adaptation is driven by the high fat intake itself, not just by restricting carbohydrates. Performance in time trials remains unchanged despite these metabolic shifts.
These findings demonstrate that high dietary fat rather than low-CHO intake contributes to reductions in mitochondrial respiration and increases in whole-body rates of fat oxidation following a high-fat, low-CHO diet.
Why this rating
Randomized crossover design with well-trained subjects, though small sample size (n=8).
Source
High dietary fat intake increases fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans
Jill J. Leckey et al. · The FASEB Journal · 2018
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