When most people think of HIIT they think of it as applicable only for cardio, yet it can also be used in weight training. After all, weight training itself is a form of HIIT—you do a set with all-out effort, rest, then do another set, rest, and repeat. Resting two to three minutes between sets, however, is too long for a training session to be considered an effective form of HIIT. But all you have to do is shorten rest periods and you're doing a kind of HIIT that burns fat.
HIIT was originally developed by track coaches to train runners, but it has crossed over to the fitness industry due to its fat-burning benefits confirmed many times over in scientific studies (see "HIIT Findings"). A lot of these studies found that subjects performing HIIT burned significantly more body fat—and in less time—than those who did steady-state cardio programs.
Why does HIIT training work better than conventional cardio for fat loss? When you do cardio at the same pace, your body adjusts itself to the workload and tries to conserve calories. (After all, your body doesn't know how long or hard you plan to work out.) Interval training forces your body to burn more calories -- and tap into fat stores -- because it has no choice. Science says so: One study at Laval University found people who performed HIIT cardio lost nine times more fat than people who performed moderate cardio at a consistent speed.
"Only doing abdominal-focused workouts, like crunches, won’t help you banish the bulge. Belly fat is simply where your body stores energy, so you need to take a whole-body approach to tackle it. HIIT training (high intensity interval training) is a great way to burn fat and get your heart rate up. Squats, burpees and treadmill sprints are all examples to try."