What happens when top athletes eat almost no carbs?
Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
VO2max improved on keto, but performance didn’t—because oxygen use at race pace got worse.
Most assume better aerobic fitness (VO2max) means better race performance. Here, it didn’t—because efficiency dropped. This decoupling is rare and counterintuitive.
Practical Takeaways
If you're an endurance athlete aiming for peak performance, prioritize carbs around intense training and races.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
VO2max improved on keto, but performance didn’t—because oxygen use at race pace got worse.
Most assume better aerobic fitness (VO2max) means better race performance. Here, it didn’t—because efficiency dropped. This decoupling is rare and counterintuitive.
Practical Takeaways
If you're an endurance athlete aiming for peak performance, prioritize carbs around intense training and races.
Publication
Journal
The Journal of Physiology
Year
2017
Authors
L. Burke, Megan L R Ross, L. Garvican-Lewis, M. Welvaert, I. Heikura, Sara Forbes, Joanne G. Mirtschin, Louise E. Cato, Nicki Strobel, Avish P. Sharma, J. Hawley
Related Content
Claims (6)
Elite race walkers who eat lots of carbs or time their carb intake during intense training get about 5-6% faster in a 10 km race, but those on a keto diet don’t get any faster.
Elite race walkers who follow a keto diet for 3 weeks start burning fat for fuel during intense exercise, and their bodies show signs of ketosis — like having 1 mmol/L of ketones in the blood — even when working hard.
When your body gets used to burning fat for fuel, it becomes better at using fat by turning up the systems that break it down and use it for energy.
Even if elite race walkers don't change their diet, their stamina can still improve after a few weeks of intense training, as long as they're eating enough calories.
Even though elite race walkers get better at using oxygen overall on a keto diet, the diet makes their bodies use more oxygen during race pace, so their performance doesn’t actually improve after 3 weeks.