If you frequently empty your liver and muscle cells of glycogen with brief, intense workouts (you burn a little bit of glucose during the long, slow stuff, too), you become adept at not only burning calories, but replenishing nutrients. Insulin will transport nutrients into your liver and muscle instead of just having them go straight to fat.

The low-intensity, long-duration cardio might help you drop weight, but a significant percentage of that might be muscle. Whereas weight training or high-intensity work (whether with resistance-training exercises or sprints) will ensure that the majority of calories you burn are fat. More importantly, it’ll build and maintain your muscle, which wil