The Myth of the Fat Burning Zone

It’s something you’ve most likely heard before - or maybe you’ve even seen a color coded posting on a treadmill or elliptical machine - the infamous “Fat Burning Zone.” If you haven’t seen or heard of this, let’s review.

The “Fat Burning Zone” is based on the idea that you can get your heart rate to a certain low-intensity level - meaning a low percentage rate of its max capacity. And if you’re able to stay in that low-intensity range for a prolonged period of time, you’ll burn the most fat. For years the treadmill and elliptical - steady state “cardio” - machines and companies touted this “fat burning zone” as the best way to lose weight. Hop on the elliptical for an hour and you’ll burn more fat that a HIIT workout.

So is there really a magical Fat Burning Zone?

Here’s where it gets complicated. And if you want even more in-depth info, check out this article. Yes, you can exercise at an intensity in which the body will be using more fat as fuel (versus glycogen, which is the stored version of carbs). The body burns a greater percentage of fat at lower intensities than at higher intensities. For example, at lower intensities, the body may burn 50 percent of the calories from fat, while at higher intensities it may only burn 35 percent.

But here’s where we’re going to burst your mystical Fat Burning Zone dreams - let’s remember that weight loss comes down to calories in and calories out.

At higher intensities you burn way more total calories (which is how you lose weight) than you do at lower intensities. This is why high-intensity intervals will always “outweigh” steady state exercise such as walking on a treadmill (without ever increasing speed or elevation) when it comes to burning calories. For example, in 30 minutes of low-intensity exercise you will burn 200 calories, and much of that will, yes, be from using fat as fuel. But in that same amount of time, you’ll burn 400 calories in a higher intensity workout. The majority of that will use the glycogen in your body as fuel. So which one would you choose? The 200 or 400 for the same amount of time? Yeah, that’s what we figured too.