The fat burning zone is your heart rate's target zone to burn the highest percentage of fat possible during exercise.
To determine your personal fat burning zone, you can use the following formula:
- Calculate your maximum heart rate based on your age.
MHR (Max HR) = 220 - Age
- Calculate the low end of your fat burning zone.
FBL (Fat Burning Low HR) = MHR x 0.60
- Calculate the high end of your fat burning zone.
FBH (Fat Burning High HR) = MHR x 0.75
For example, if you are 40 years old your MHR will be 180 beats per minute (bpm). This means that your fat burning zone will be between 108 bpm (FBL) and 135 bpm (FBH).
The fat burning zone is a deeply debated subject since working in this zone maximizes the percentage of fat calories burned and not the total amount of calories.
In other words, a more intense workout (higher average heart rate) will burn more total and fat calories than a same length workout exclusively done in the fat burning zone.
For example, let's compare a high intensity workout performed above the fat burning zone with a workout performed exclusively in the fat burning zone.
Above Fat Burning Zone (AVG HR of 150 bpm):
- Total calories burned: 600
- Percentage of fat calories: 50%
- Fat calories burned: 300
Fat Burning Zone (AVG HR of 125 bpm):
- Total calories burned: 400
- Percentage of fat calories: 65%
- Fat calories burned: 260
However, you could surpass the amount of fat calories burned by working out for a longer period of time in the fat burning zone, since it isn't as physically demanding as working out at higher intensities.
All this being said, to maximize your caloric burn, you can choose to either perform a higher intensity workout or a lower intensity workout for a longer duration.
Therefore, to achieve your weight loss goals, it's important that you find the maximum SAFE intensity at which you can work out for the longest duration in order to produce the highest total caloric burn possible during your workout.