Chances are you have heard or read something about the “fat burning zone” or if you belong to a gym, there is probably a chart on the wall by the cardio machines telling you about different heart rate zones, including the fat burning zone. The fat burning zone appears to be self-explanatory, but it is often interpreted incorrectly. Misunderstandings about the fat burning zone and its implications have resulted in confusion about how to exercise for optimal fat loss.
The natural place to start is by explaining what the fat burning zone actually is. The fat burning zone describes the cardiovascular exercise intensity level where you burn the highest percentage of calories from fat. The zone refers to a heart rate range, which is often said to occur around 50-60% of your maximal heart rate, although these numbers can vary from person to person.
The important thing is the fat burning zone occurs at lower exercise intensities. Generally speaking, easier exercise results in a higher percentage of fat calories being burned during the exercise. As exercise difficulty increases, fewer calories are burned from fat and more calories are burned from carbohydrates. The fact that a higher percentage of fat is burned at lower exercise intensity levels has led people to think that performing easy workouts is the best way to lose fat.
While it sounds reasonable that burning a higher percentage of fat calories leads to greater fat loss, it is an oversimplification that ignores the big picture. Exercising in the fat burning zone only means you burn a high percentage of calories from fat, but it does not tell you anything about how much fat or how many calories you actually burn.
When exercising in the fat burning zone, intensity level is relatively low and as a result, the total calories and fat calories burned are also low. Exercising at heart rate levels higher than the fat burning zone will burn more total calories and may even burn more fat calories as well. Most importantly, even if you burn more fat calories by training in the fat burning zone, it does not really matter, because the total number of calories burned is more important for fat loss than the fat calories burned.
This may not be intuitive, but as far as your body is concerned, a higher number of total calories burned will stimulate greater fat loss than a lower number of calories burned, regardless if the calories are from fat or carbs. In the end, if you do not burn more calories than you consume, you have no chance of losing fat, even if 100% of the calories burned during your workouts are from fat.
Another important thing to keep in mind is that unless you are an elite athlete that trains for many hours every day, the calories burned during your workouts is going to be very small compared to the calories burned by your metabolism. As a result, your focus should be less on what percentage of fat calories are burned during your workout and more on what you can do to increase the amount of calories your body burns throughout the day.
This leads to another problem with training in the fat burning zone. The low intensity exercise performed in the fat burning zone not only burns fewer calories than challenging exercise, but it also has very little if any impact on increasing your metabolism or burning extra calories after you are finished exercising.
You have probably heard that exercising causes your body to burn more calories throughout the day, but there is only a significant added calorie burning effect after challenging workouts. There is still some debate about the exact cause the calorie burning increase, but it is definitely linked to the body’s need to recover after strenuous exercise. Since exercising in the fat burning zone is not too difficult for your body, the stimulus is not there for your body to burn extra calories throughout the day.
Another issue with the fat burning zone is that it is simply is not challenging enough to cause significant improvements in fitness. As your fitness level increases, you will be able to perform more challenging workouts that burn even more calories, both during and after exercise. In addition, you may gain some fat-free mass (muscle), which increases your metabolism, so you will burn more calories all day, every day.
When looking at the big picture, it becomes clear that exercising in the fat burning zone should not be your priority if you want to maximize your fat loss. However, if you are still not convinced, I have one question for you. How many people have you seen who lost a lot of fat and got into great shape by doing easy workouts and training in the fat burning zone?
My guess is not very many, because it is more the exception than the rule. When it does happen, it almost certainly has more to do with the person’s genetics or nutritional program and not because they exercise in the fat burning zone. If anything, results improve when at least some workouts are at higher intensity levels.