Fat Adaptation Does Not Eliminate Carbs for Endurance Athletes — image accompanying Marathon Handbook's report. Image accompanying Marathon Handbook’s report; reduced and presented for news commentary with the attributed report. View the complete source report.
A study tested the impact of low-carb diets on endurance performance. Marathon Handbook reports that triathletes maintained performance on low-carb diets but still benefited from small carbohydrate intake.
The trial involved 10 male triathletes on high-carb and low-carb diets. They performed cycling tests at 70% VO₂ max, consuming either placebo or 10 grams of carbohydrate per hour. Marathon Handbook found performance remained stable on low-carb diets with carbohydrate intake. Read more culture coverage.
The study highlights that fat adaptation does not eliminate the need for carbohydrates. Even with fat adaptation, a small carbohydrate dose improved performance. Marathon Handbook emphasizes the importance of carbohydrate availability for prolonged, moderate-intensity exercise. Related: Brain Stimulation Fails to Boost Endurance in Study.
This original Runner World brief is based on reporting from Marathon Handbook. Visit the source for its complete reporting, context and any later corrections.
Reader questions
Questions about this report
What should runners know about Fat Adaptation Does Not Eliminate Carbs for Endurance Athletes?
Study shows small carbohydrate intake still benefits triathletes on low-carb diets. A study tested the impact of low-carb diets on endurance performance. Marathon Handbook reports that triathletes maintained performance on low-carb diets but still benefited from small carbohydrate intake.
When did Runner World publish this culture brief?
Runner World published this brief on October 9, 2026. The underlying Marathon Handbook report was dated October 9, 2026.
Where can readers find the complete original report?
This summary is based on reporting from Marathon Handbook. The attributed source link in the article leads to the publisher’s complete report.
THE WEEKLY BRIEFING
Start the week a step ahead.
A concise edit of the running stories worth knowing, sent every Monday.
