For years some fitness magazines and fitness instructors preached about the advantages of exercising at a low intensity or in the “fat burning zone.” The theory was that because your body uses a high percentage of fat as its fuel during long, slow aerobic workouts, you would burn more body fat by exercising at a slower pace, rather than at a faster tempo, where carbohydrates are the primary fuel source. There is no question that fat supplies a relatively large percentage of the energy required during prolonged, low intensity aerobic exercise. But at this low intensity, relatively few total calories are burned. By contrast, higher intensity aerobic exercise uses a smaller percentage of fat but results in a greater number of calories being burned. When all the calculations are done, the numbers show that more fat is burned during the higher intensity exercise.
Does this mean that all exercisers looking to burn fat should be exercising at high intensities? Not at all. If you have been sedentary, doing high intensity exercise—exercising at a target heart rate of 70% to 85%— will be impossible to keep up for an extended period of time. It makes sense that lower intensity exercise—at a target heart rate of 50% to 60%—is more effective and appropriate in the early stages of training. (Refer to Target Heart Rate in this section for more detail.)
- In reality, whatever kind of exercise you will continue to do on a regular basis is the best exercise for burning fat. The more calories you burn the better, as long as you don’t over do it. If you prefer low intensity activities, that’s great. But you need not limit yourself to that level if you are in good shape and enjoy working harder.
- It’s also important to remember that the fat burning power of exercise doesn’t end when your workout does. Regular aerobic exercise raises your metabolism so that you continue to burn calories at a higher rate for up to several hours after your workout.
- If you want to become a better “calorie burning machine” once you have been exercising on a regular basis, use the fol-
- Start by developing a reasonable level of aerobic fitness. Exercise three to four times per week for 25 to 40 minutes
at a moderate intensity (60% to 70% of your target heart rate.
- Gradually increase the exercise duration to 50 to 60 minutes at least three to five days per week and raise the intensity as high as you can safely sustain it (no higher than 85% of target heart rate).
- Include strength training twice a week to increase your muscle size or mass. Remember, muscle is denser than fat and takes up less room, so when we use words like size and mass, it doesn’t mean big, bulky muscles unless you especially train to achieve that.
- Allow at least six months to realize significant body changes. You may notice small things at first; for example, your abdominal muscles may seem tighter or your legs may seem stronger. However, you have to be consistent in order to see significant changes such as weight loss. Keep in mind that you may find exercise more enjoyable at a more comfortable pace than we’ve suggested above. You’re also more likely to stick with your program if you don’t.