Shattering the myth of the fat-burning zone

By Sabrina Gonzalez | Photo by Japheth Mast/Unsplash

Contemplating on the best way to shed off all those holiday calories? I’m sure you’ve come across the myth of the so-called fat-burning zone. Many sources state that low-intensity exercise burns more fat than high-intensity exercise. But is that really true? Is there really such a thing as the fat-burning zone?

Well, the short answer is, no. But it isn’t completely false either. Let us clear up this misinformation, and reveal the truth behind the myth.


What is the fat-burning zone?

First of all, let us define the fat-burning zone. The fat-burning zone has been defined as the amount of activity that allows you to achieve around 60 to 70 percent of your maximum heart rate. This generally corresponds to moderate intensity workouts. Attaining higher heart rates, up to about 85 percent of your maximum heart rate, puts you in what is termed as the cardio zone.


The science behind the fat-burning zone

There is some scientific basis to the idea of the fat-burning zone. Fat is indeed the main source of calories burned during exercises at low intensity and at rest. At these times, the body undergoes aerobic metabolism–fat makes use of oxygen in order to supply the necessary fuel for the body. Aerobic metabolism tends to be slower, and is ideal for prolonged, steady activities.

Higher intensity activities meanwhile require a faster source of energy. Carbohydrates are easier to break down and do not require oxygen to be metabolized; they become the primary source of fuel during these times. However, this anaerobic metabolism cannot be sustained for long periods of time because metabolic by-products tend to accumulate and prevent the body from carrying out further activity.


The truth about the fat-burning zone

While it is true that you are burning a higher percentage of fat at lower intensities, the overall amount of calories you burn is still less. Thus, in order to burn more total calories, you should exercise at higher intensities. High-intensity exercises also help increase your metabolism, allowing you to burn calories even after you have finished your workout.

Let us use numbers to make it more transparent. For example, at a lower intensity, you burn 70 percent fat and 30 percent carbohydrates, while at a higher intensity, it’s the opposite. Suppose walking for an hour burns 100 calories while running for half an hour burns around 300. Thus, walking allows you to burn 70 calories of fat and 30 calories of carbohydrates, while running allows you to burn 90 calories of fat and 210 calories of carbohydrates. Overall, you still burn more fat calories at higher intensities even if it corresponds to a lower percentage of the total.


Exercise with caution

Given all of these, you would therefore be able to lose weight faster if you do high-intensity exercises. However, it is important to remember that limiting your workouts to high-intensity activities only can easily result in overtraining, burnout, and injuries. Experts suggest performing high intensity exercises two to three times a week and alternating these with low-intensity activities. This will ensure that your body is well-balanced, helping build your endurance while allowing you to burn fat faster, regardless of whether you are in the fat-burning zone or not.

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