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Should you worry about the ‘fat-burning zone’?

Fatburning exercise

Is this really fat burning?

As I’ve just learned from a friend, people are apparently still buying into the myth that low-intensity exercise is better for fat loss because it’s performed while in a “fat-burning heart-rate zone.”

Everybody was talking about this in the 1980s, and if you jump on aerobic equipment built in that era, you’ll still see that those machines have options for choosing a workout in the “fat-burning zone.”

Here’s why you shouldn’t give a rip about trying to enter the “fat-burning zone.”

All exercise—all body movement, in fact—is fueled by a combination of fat and carbohydrate. The “fat-burning zone” argument is based on the notion that low-intensity exercise burns a greater proportion of fat than high-intensity exercise.

This is true.

In fact, you burn a higher percentage of fat and a lower percentage of carbohydrate (blood sugar) while sleeping or sitting in a chair than you do running or otherwise exercising intensely.


Converting fat to usable energy is a relatively slow, complicated process—whereas putting blood sugar to use is much simpler and faster.

So when your body’s energy needs are high—like when you’re doing fast aerobic dance moves, lifting weights intensely, running, rowing, or otherwise going all out—your body relies on carbohydrate.

But when you’re vegging out on the couch, you don’t need much energy. A slow, steady source like the fatty acids from your muffin top can easily fill the bill.

Now let’s think about why you’re exercising. You want to be healthy and feel good and live longer, yeah? But I suspect you want to burn calories too.

It’s important to know that whether the calories you burn during the exercise come from blood sugar, glycogen (sugar in a form that can be stored in your muscles and liver), or fat, they’re all burned calories. If you create a caloric deficit by consuming less and burning more, you’re going to lose fat.

My point, in the most obvious way I can express it: when you burn calories via exercise, it is irrelevant which energy source your body uses during the exercise. It’s the daily total that counts: energy intake versus outgo.

Are you in a caloric deficit because you 1. ate less, 2. burned more through movement, or 3. both? If yes, you will lose fat.

People who accept the “fat-burning zone” myth will tell you the best way to burn fat is to exercise at low intensity—generally 60 percent to 65 percent of your maximum heart rate. There’s nothing wrong with exercising at that intensity level, especially if you have lots of time on your hands.

If, however, you don’t have oodles of spare time and want to burn calories quickly, it makes more sense to work harder and shorter.

Here’s a quick example. A 150-pound person who walks for 30 minutes at 3 miles per hour (mph) will burn about 148 calories. The same person who runs for 30 minutes at 5 mph burns about 288 calories.

Doing that 30-minute walk four times a week will burn 592 calories, or about 2.7 ounces of fat; running four times weekly for the same length of time requires 1,152 calories, thus burning nearly 5.3 ounces of fat.

Which sounds better to you?

Interested in more fitness and fat-loss tips? Visit, follow me on Twitter, or connect with me on Facebook.

Mary is a writer, editor, blogger, webmaster, bodybuilder, and singer living in Tennessee, USA. She is an NSCA Certified Strength and Conditioning Specialist.


Mary C. Weaver, CSCS

I'm a weight-loss and body-transformation coach for women---and I want to share my best weight-loss strategies with you! Click the link to learn more about my Body-Transformation Bootcamp program!

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