Unfortunately, there isn't one exercise or piece of equipment that will spot-reduce fat from your belly. What you need to do is fast-paced cardio to burn calories, which will reduce your overall body fat and slim down every part of your body, including your tummy. Skip the leisurely walks with your dog, and choose the types of cardio that burn the most calories, such as biking, running, and jumping rope. Do 60-minute sessions five times a week to really notice a difference.