You don't need to spend countless hours at the gym to get in shape. High-intensity interval training is the best way to burn fat. If you don't have access to a stairmaster, this workout can be done on an elliptical or treadmill. Push yourself by pedaling as fast as you can on the level indicated (on elliptical), or on the highest speed you can run (on treadmill). This workout will only take you about 20 minutes!