Eating fat for a week makes your body burn fat better, but you can't sprint as hard
Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Cyclists ate either a high-fat or high-carb diet for 6 days, then loaded up on carbs for 1 day. They rode 100 km and did sprints. The high-fat diet made their bodies better at burning fat, but they couldn't go as fast in the sprints.
Surprising Findings
Sprint power dropped even after full carb loading and with no change in effort perception or muscle activation.
Most assume that loading carbs the day before fixes any fuel issues—even after fat adaptation. This study shows otherwise: the body still underperforms in high-intensity efforts despite available carbs and normal neuromuscular signals.
Practical Takeaways
Avoid high-fat diets in the week before a race if your event requires sprints, breakaways, or surges.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Cyclists ate either a high-fat or high-carb diet for 6 days, then loaded up on carbs for 1 day. They rode 100 km and did sprints. The high-fat diet made their bodies better at burning fat, but they couldn't go as fast in the sprints.
Surprising Findings
Sprint power dropped even after full carb loading and with no change in effort perception or muscle activation.
Most assume that loading carbs the day before fixes any fuel issues—even after fat adaptation. This study shows otherwise: the body still underperforms in high-intensity efforts despite available carbs and normal neuromuscular signals.
Practical Takeaways
Avoid high-fat diets in the week before a race if your event requires sprints, breakaways, or surges.
Publication
Journal
Journal of applied physiology
Year
2006
Authors
L. Havemann, Sacha West, J. Goedecke, Ian A. Macdonald, A. Gibson, T. D. Noakes, E. Lambert
Related Content
Claims (6)
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.
If elite male cyclists eat a super high-fat diet for six days and then carb-load for one day, they’ll perform worse in sprints—even though they don’t feel more tired, their heart rate doesn’t change, and their muscles fire the same way.
If elite male cyclists eat a super high-fat diet for 6 days before carb-loading for a day, they’ll feel just as fast over a long 100-km ride — but they’ll have less power for short, intense sprints compared to when they eat a high-carb diet first.
If male cyclists eat a super high-fat diet for six days, their body's 'fight or flight' system might get a bit more active — and that change doesn’t go away right after they start eating carbs again.
If elite male cyclists eat a super high-fat diet for six days, their bodies get better at burning fat for fuel — even when they switch back to eating lots of carbs for a day.