Cardio intervals, or short sprints in between slower recovery periods, are better at helping you lose weight than steady-state cardio because they force your muscles to work harder without adequate oxygen, a process called anaerobic conditioning. This helps your muscles burn more fuel, perform better, and grow in the long run and can even cause certain gene changes in your body that fire up your metabolism. And since bigger muscles equal more fat burn, interval training is a smart strategy to incorporate into a few cardio workouts each week.