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 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 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.

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 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.

Whether you eat carbs, protein, or nothing before a bike ride, you don’t feel hungrier during or after the ride — your appetite stays about the same.