5-Marathons-in-5-Days-Fuelled-only-by-Water-with-Alex-McDonald Chief Nutrition

5 Marathons in 5 Days Fuelled only by Water with Alex McDonald

Updated: Jul 10, 2025Veronika Larisova

In this episode of Chief Life, we sit down with Alex McDonald, who completed an incredible feat—running 5 marathons in 5 consecutive days while fasted, consuming only water and electrolytes. Alex has been following a low-carb diet for 14 years and a strict carnivore diet for the past five, challenging conventional wisdom on endurance fuelling.

We discuss:
  • Why he chose to run 5 marathons fasted
  • His transition from keto to carnivore and how it impacts his performance
  • Training, nutrition, and preparation for extreme endurance challenges
  • How his body responded—blood markers, body composition, HRV, and recovery
  • The role of fat adaptation in endurance performance and whether carb-loading is necessary
Alex shares his key takeaways from the experiment and whether he plans to take on more endurance challenges in the future. If you’re curious about low-carb endurance performance or considering testing your own limits, this episode is packed with insights!

 

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