We recently performed a study looking at the influence of different pre-exercise nutrition choices on how much fat we burn during exercise, and high-intensity interval training capacity.
Seventeen well-trained male cyclists and triathletes came into the lab on three occasions to perform 20 min of sub-maximal cycling, where we measured things like fat oxidation, followed by 6×3 min intervals to see how what they ate beforehand influenced the exercise session. One session was performed in the overnight-fasted state, once following a carbohydrate-rich breakfast, and once following a protein-rich breakfast.
Overall, exercising in the overnight-fasted state increased fat oxidation during sub-maximal exercise compared with exercise following a carbohydrate-rich breakfast, and pre-exercise protein ingestion allowed similarly high levels of fat oxidation. Surprisingly, there were no differences in perceived exertion, hunger, or performance.
I made a short video to highlight some of the key results…