If you’re overweight and looking to change your lifestyle, you may be wondering which type of exercise is most effective for you. Some people favor fast, intense workouts, while others prefer low-intensity, longer-duration sessions. But why is it beneficial to use your body’s fat to fuel cardio exercise, especially if you’re overweight? In this article, I will provide answers to that question! During cardio exercise, your body primarily uses two energy sources: carbohydrates and fats.