Effect of a Ketogenic Diet on Submaximal Exercise Capacity and Efficiency in Runners

A 31-day ketogenic diet preserved mean submaximal exercise capacity in trained endurance athletes.

• Exercise efficiency was impaired on a ketogenic diet, particularly at intensities above 70% of maximum oxygen uptake.
• Increased energy expenditure and oxygen uptake during exercise on a ketogenic diet could not be explained by changes in respiratory exchange ratio.
• Exercise efficiency remained stable when exercising at less than 60% of maximum oxygen uptake.
• Time-to-exhaustion was similar for both dietary adaptations, indicating no significant changes in endurance performance.
• The relationship between respiratory exchange ratio and time-to-exhaustion indicated individual variability in endurance responses to the ketogenic diet.

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