Early-morning exercise stokes your metabolism and helps you burn more calories for the rest of the day. In fact, if you can get in 45 minutes, then Appalachian State University research shows you could experience a metabolic spike that torches an additional 190 calories over the rest of the day. Try a circuit of the basics like jumping jacks, squats, and push-ups. And for mornings you really don't have any time, try this 2-minute fat-burner.