Here’s a really interesting study result for you.
When researchers studied the effect of various diets on cycling performance they found no difference between people who fasted 24 hours the day before versus people who overate by double their daily calorie needs the day before.
While this is good news (fasting doesn’t affect next day sport performance), what really stood out to me was that the people who fasted burned the most fat during their cycling test.
While this seems like a no-brainer, there is a catch – They all ate breakfast before their exercise test.
The subjects in this study fasted for 24 hours, then ate a breakfast of around 500 Calories (consisting of Ham, Pancakes, Syrup and Orange juice), waited for two hours, then did a cycling test where they still used more fat as fuel than when they did the same cycling test before without fasting for 24 hours before hand.
This suggests that the preference for using fat as a fuel that is caused by a 24-hour fast may carry over into the next day, even when a meal has been eaten and exercise is being performed.
*Obesity (Silver Spring). 2018 February ; 26(2): 368–377.