INCREASE YOUR INTENSITIES
An engine running at full speed burns a lot of fuel!” This is a good way to picture the fat-burning mechanism during an intense running session.
A strenuous interval workout requires a lot of energy. While it is true that the percentage of fat burned in the metabolic process is quite high during long slow runs, the total daily energy expenditure, and thus the number of calories burned, is relatively low due to the low intensity of the workout.
In the case of high-intensity running workouts, like intervals, the percentage of fat burned in the metabolic process is significantly lower, but the total daily energy expenditure and the calories burned are many times higher.
Furthermore, the “afterburn” effect is much higher during your recovery from a high-intensity workout than a low one. “But be careful: intense running workouts are very hard on your body. For this reason, you shouldn’t do more than once per week.