Fat Burning Made Simple
“How can I lose this fat?”…This seems like a simple enough question, right? It’s also one that is asked time and time again, yet so many people still have issues with weight and excess fat. In this article, we seek to answer the not-so-simple question in a way that is clear, easy to understand, and practical.
Throughout the day, whether we are participating in activity or not, our bodies are burning calories (read A Calorie Primer). Proteins, carbohydrates, and fats serve as the fuel for our bodies. While all three of these nutrients provide fuel at any given time, our level of activity determines the percentages in which these nutrients are used. For example, while resting, 70% of the calories burned come from fat. When engaging in high intensity exercise, almost all of our energy comes from carbohydrates that have been stored in the body as glucose.
When our bodies are completely at rest (sleeping, sitting on the sofa, etc.) the average heart rate varies between 30-40% of our maximum heart rate. Although fat calories make up a greater percentage of total calories burned when the body is at rest, overall calorie burn is much lower than calorie burn during exercise. Therefore, fewer total fat calories burned are burned while we rest.
What is the fat burning zone?
As your activity level increases above a resting state, your heart rate increases as well. The heart rate range of approximately 60-75% of your maximum heart rate (defined as 220 minus your age) is known as the “fat burning zone.” In this zone, the body burns a greater percentage of fat calories than it does at higher intensities of exercise. Don’t be confused, however. Even though the percentage of fat calories is higher in the fat burning zone, this lower intensity exercise burns less total calories than more intense exercise.
What is the aerobic (or cardio) zone?
The aerobic zone is the heart rate range (70-85% of maximum heart rate) that is most beneficial to your cardiovascular system. Exercise in the aerobic zone is more difficult than that in the fat burning zone, and therefore, cannot be performed as long as exercise at a lower heart rate. Within the aerobic zone, the primary supplier of fuel shifts from fats to carbs. Above this zone, fat burning is minimal.
Which is better… higher intensity exercise or lower intensity exercise that burns higher percentages of fat?
Each type of exercise has its place. The tradeoffs occur when the length of your workout and the intensity are adjusted. Exercise in the fat burning zone can be sustained for longer periods of time. Higher intensity workouts in the aerobic zone burn higher numbers of calories, but may be difficult to sustain. The exact number of calories burned in each case will depend on several factors, including gender, weight, body composition, and fitness level.
If your goal is to lose weight, total calorie burn should be your concern. In this case, higher intensity workouts in the aerobic zone are recommended. If, however, you are within a normal weight range and simply wish to lose fat, the fat burning zone is a more appropriate choice. It is important to remember that the workout you choose should always include an adequate warm-up and post-exercise stretch routine, and should be part of a larger plan where several types of exercise are included.
What’s the best way to maximize fat burn and get a good aerobic workout?
You may have noticed that there is a 5% overlap (70-75% of your maximum heart rate) between the fat burning and aerobic zones. Exercise intensity at this rate may be a good way to reap the benefits of both zones. Although total calorie burn could be higher with a higher intensity of exercise, this moderate level of exercise will allow you to burn the maximum percentage of fat calories and still reap the benefits of cardiovascular exercise.
Another way to take advantage of fat burning and aerobic exercise is to perform interval training. Interval workouts consist of short periods of high intensity exercise broken up with equal or longer periods of low intensity work (in the fat burning zone). Interval workouts typically last for shorter periods of time than traditional aerobic workouts, but provide high rates of calorie burn. The alternating intensities provide time in both the fat burning and aerobic zones. Interval workouts also increase calorie burn for several hours after your workout is complete.
The high intensity portion of your interval workout could last for 30 seconds to 3 minutes, depending on your fitness level. The low intensity portion should last 1-3 times as long as the high intensity portion. Because interval training can include exercise at near maximal levels of performance, it is important to have a strong aerobic base before trying to perform an interval workout. A good rule of thumb is that you should be able to exercise in the aerobic zone for the length of time that your entire interval workout will last.
Are there other ways to burn fat?
Wouldn’t it be nice if we could burn fat without any effort? Well, we can! …(kind of). Remember, while the body is at rest, 70% of the calories burned are fat calories. We can indirectly control how many calories our bodies burn while resting by increasing our lean muscle mass. Muscle is more metabolically active than other elements in the body, and therefore, burns fat to sustain itself. Earlier we mentioned that body composition plays a part in determining how many calories are burned at any given moment. Increase the amount of muscle you have and burn more fat while you sleep!
Exercise in the fat burning zone when…
- Higher intensity workouts are not recommended by your physician
- Your current aerobic capacity doesn’t allow you to exercise at higher intensities
- Physical condition or injury prevents higher intensity exercise
- You prefer a lower intensity workout
- Training for distance or endurance
- You are within normal weight standards and you wish to target fat loss vs. weight loss. (Note: Individuals who are overweight or obese should focus on overall weight loss.)
- To prevent overtraining that could be caused by constantly performing high-intensity exercise
Exercise in the aerobic zone …
- To improve cardiovascular function
- When weight loss is a goal
- When the amount of time available for exercise is limited