The Study
Metabolic characteristics of keto-adapted ultra-endurance runners.
This study looked at two groups of super-fit runners — one eating lots of carbs and one eating mostly fat — and found their bodies burned fat differently during exercise. But it didn’t change what they ate to see if that caused the difference, so we can’t say the diet made the change happen.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
Some elite runners eat mostly fat and very few carbs, and their bodies get really good at burning fat during long runs.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 541 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This means their bodies can run long distances using mostly fat without needing to carb-load, even though they still use muscle glycogen the same way as carb-eaters.
- 2Fat-burning runners burned fat at 1.54 g/min (vs.
- 30.67 g/min in carb-eaters), used fat for 88% of energy (vs.
- 456%), and still used the same amount of muscle glycogen during and after a 3-hour run.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Metabolism: clinical and experimental
Year
2016
Authors
J. Volek, Daniel J. Freidenreich, Catherine Saenz, Laura J Kunces, Brent C Creighton, Jenna M. Bartley, P. Davitt, C. Muñoz, Jeffrey M. Anderson, C. Maresh, E. Lee, M. Schuenke, Giselle A Aerni, W. Kraemer, S. Phinney
Related Content
Claims (5)
Ultra-endurance runners who eat a low-carbohydrate diet for a long time reach their highest rate of fat burning at 70.3% of their maximum oxygen uptake, while those on a high-carbohydrate diet reach it at 54.9%.
Ultra-endurance runners who eat a diet that is mostly fat and very low in carbohydrates burn fat at a rate 2.3 times higher during maximum effort than runners who eat a diet high in carbohydrates.
Ultra-endurance runners who follow a long-term low-carbohydrate diet burn fat at a rate 59% higher during 180 minutes of steady endurance exercise at 64% of their maximum oxygen uptake, and derive 88% of their energy from fat, compared to runners on a high-carbohydrate diet who derive 56% of their energy from fat.
Ultra-endurance runners who eat a low-carbohydrate diet for a long time burn more fat during exercise than those on a high-carbohydrate diet, but their muscle glycogen levels at rest and during a 3-hour run are the same.
On a low-carbohydrate diet, muscle glycogen is completely restored within 24 hours after resistance training, and consuming large amounts of carbohydrates does not improve this recovery process.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.