There is no better way to burn fat and build muscle at the same time than kettlebell swings, snatches, and clean and jerks. These ballistic exercises work your body as one unit and require a great deal of hard work. The harder you work the more calories you burn. This is why sprinters are ripped to shreds and marathon runners have a skinny-fat look.
As effective as sprinting is, ballistic kettlebell exercises such as high rep snatches (20 reps or more per set) make sprinting look like a walk in the park. High rep snatches work more muscle groups than sprinting and will build strength in the lower back, shoulders, and hip flexors. Its kind of fun too!
For best results, make sure you follow a good total body routine and diet (you get both in my workout plan). It may also help to try a good fat burner like TEA REXX, it is what I use to help me stay ripped.