"Fat burn zone" a myth?

Dreysander

So my Fitbit charge HR will tell me when my heartrate is in "fat burn" vs "cardio" zones whenever I am exercising. Is there any legitimacy to the targeted heartrate for fat burn thing?

Sued0nim

For fat burn..no ...I'm surprised that a fitbit would do that

Training zones yes

amusedmonkey

The naming has its reasons, but many get confused by it and think it means what it doesn't. "Fat burn" zone is when your body relies more on fat for fuel. What does it mean in context of weight loss? Nothing! It does have a significance in sports because it can be used to aid performance and recovery since it doesn't use as much glycogen as higher intensity (an important resource for endurance athletes.) "Cardio" zone mostly lets you know that you can improve your cardiovascular fitness effectively by working at this intensity. Improved cardiovascular fitness allows you to burn more calories. There is also a 3rd exercise zone in Fitbit and that's "peak". It means you are burning predominantly carbohydrates and are at a level that is too taxing for the body to maintain for long. It has the most potential to improve your cardio fitness.

If you had a workout that is mostly in the cardio zone with quite a few peak periods thrown in, it makes sense to have one that is mostly in the fat burning zone the next day if you aren't resting. This allows your body to recover and replenish. If you are a totally out of shape beginner, it would also make more sense to keep your workouts in the fat burning zone for a while until your body starts adapting to the newly introduced stressor.

These are basically data points, nothing more nothing less. They mean nothing for weight loss but may be useful to optimize training.

Here is what Fitbit has to say about zones:

WHAT ARE HEART RATE ZONES?

Heart rate zones can help you optimize your workout by targeting different training intensities. Your zones are calculated based on a percentage of your estimated maximum heart rate. Fitbit calculates your max heart rate with the common formula of 220 minus your age. The illustrations below provide examples for each zone. Note that the appearance of the heart icon on your tracker tells you your zone at a glance. For more information about zones, see the American Heart Association's Target Heart Rates article.

PEAK ZONE

Peak zone, which means your heart rate is greater than 85% of maximum, is the high-intensity exercise zone. The peak zone is for short intense sessions that improve performance and speed.


CARDIO ZONE

Cardio zone, which means your heart rate is 70 to 84% of maximum, is the medium-to-high intensity exercise zone. In this zone, you're pushing yourself but not straining. For most people, this is the exercise zone to target.


FAT BURN ZONE

Fat burn zone, which means your heart rate is 50 to 69% of maximum, is the low-to-medium intensity exercise zone and may be a good place to start for those new to exercise. It’s called the fat burn zone because a higher percentage of calories are burned from fat, but the total calorie burn rate is lower.

OUT OF ZONE

When you’re out of zone, which means your heart rate is below 50% of maximum, your heart rate may still be elevated but not enough to be considered exercise.

So no, it's not a myth, but there was a time when poor understanding of the facts behind the name gave rise to some myths.

SingingSingleTracker

Dreysander wrote: »

So my Fitbit charge HR will tell me when my heartrate is in "fat burn" vs "cardio" zones whenever I am exercising. Is there any legitimacy to the targeted heartrate for fat burn thing?

The body will burn fat for fuel in all of the heart rate zones that one trains. The difference being, some of the zones burn more fat and less carbohydrates and protein than others and vice versa.

Somewhat of a reasonable explanation here...

http://www.weightlossforall.com/exercise-fuel.htm