Metabolic characteristics of keto-adapted ultra-endurance runners

Peak fat oxidation in ultra-endurance athletes on a low-carbohydrate diet is 2.3-fold higher than that of those on a high-carbohydrate diet.

• Fat oxidation in the low-carbohydrate group peaked at 1.54 g/min, occurring at 70.3% of VO2max.
• In contrast, the high-carbohydrate group peaked at 0.67 g/min at 54.9% of VO2max.
• Mean fat oxidation during submaximal exercise was 1.21 g/min for the low-carbohydrate group, compared to 0.76 g/min for the high-carbohydrate group.
• The relative contribution of fat as fuel during submaximal exercise was 88% for the low-carbohydrate group, compared to 56% for the high-carbohydrate group.
• There were no significant differences in resting muscle glycogen levels or depletion rates after 180 minutes of running and subsequent recovery.

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