Intensity is best

You may have heard that long, slow aerobic workouts are best for fat burning. That's partly true--you burn a higher percent of fat at an easy pace of less than 70 percent of your max heart rate. But you burn more total calories when you exercise more intensely, so even though you're burning a lower percent of fat, you're burning more total fat when you pick up the pace to 75 to 85 percent of max.