The Study
Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance.
This study is like a carefully run experiment where each cyclist tried two different diets in random order. Because it was randomized and controlled, it can show that the diet likely caused the changes in sprint performance, not just that they happened together.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
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.
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 550 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This means that even if you feel fine, a fat-based diet might secretly limit your ability to go all-out for short bursts, which could matter in races.
- 2After the high-fat diet, sprint power dropped by a significant amount.
- 3The 100-km ride time was the same.
- 4Their bodies burned more fat (lower RER).
- 5They felt just as tired and their muscles worked the same, even though they were slower in sprints.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
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.
If a male cyclist eats a super high-fat diet for 6 days and then loads up on carbs for 1 day, it won’t slow them down in a 100-km race compared to eating lots of carbs all along.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.