HIIT Workouts The most effective type of cardio that's proven to target belly fat is high-intensity interval training (HIIT). And no need to suffer for hours at the gym. "The whole workout, including warmup, doesn't need to be more than 45 minutes to be effective," says fitness instructor John Kersbergen. He added that three to four times a week is enough. Here are some HIIT workouts you can try: This 45-Minute HIIT Workout Will Help Shrink Your Belly Feel Your Strongest From This 45-Minute Flat-Belly Running and Strength Workout 30-Minute Cardio and Core Workout For Strong, Hot Abs This CrossFit HIIT Workout Is Just 12 Minutes, but You'll Be Toast Afterward 30-Minute Jumping Rope and Strength Training Mashup Image Source: POPSUGAR Photography