Researchers have confirmed that at lower intensities (50% VO2max), a greater percentage of energy comes from fat than at higher intensities (70% VO2max). However, as long as workouts are the same length, the total energy expenditure will be greater at a higher training intensity than lower training intensity.

The best strategy for optimal fat-calorie burning without increasing the risk of injury, is to integrate and balance the low-to moderate-intensity, long duration workouts with high-intensity workouts.

The bottom line:
“To burn more fat, burn more calories.”