Research
Macro partitioning
Increasing fat availability (via elevated plasma free fatty acids) downregulates carbohydrate oxidation in skeletal muscle during exercise, primarily by inhibiting glycogen phosphorylase (PHOS) activity through reduced accumulation of ADP and AMP.
If you consume a high-fat meal or supplement before exercise, your body will burn more fat and less glycogen. However, this 'fat sparing' effect does not necessarily improve performance. For optimal performance, especially at high intensities, relying on carbohydrates is still superior.
GoodSupportsHIGH confidence
Exercising at this high intensity in the presence of artificially elevated FFA levels decreased net glycogen use by approximately 50 % in the initial 15 min of exercise and increased fat oxidation by approximately 15 % during 30 min of exercise [8, 10]. The muscle contents of free ADP and AMP, activators of PHOS, were significantly reduced (increased less) in the high FFA condition during exercise, and appeared to explain the decreased PHOS activity and glycogen use.
Why this rating
Based on human studies using lipid infusion and heparin (refs 8, 10).
Source
New Insights into the Interaction of Carbohydrate and Fat Metabolism During Exercise
Lawrence L. Spriet · Sports Medicine · 2014
narrative_reviewCited 269×
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