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You may have seen “fat burning zone” markings on elliptical, treadmills, or other cardio equipment that tracks your heart rate. But what do they mean, and why is the “fat burning zone” less intense? Shouldn’t more intense exercise burn more fat?

Exercising at a lower intensity will result in a higher percentage of calories burned come from fat. However, percentages aren’t everything. A combination of more intense exercise and staying active throughout the day will provide the best results.

What is the “Fat Burning Zone”?

The theory behind the Fat Burning Zone is based in science, but often the application of that science is misguided. At rest (sitting on the couch) your body gets a higher percentage of its fuel from fat (~85%) rather than carbohydrates (~15%). Exercises at a lower intensity actually burn a higher percentage of fat. As you increase the intensity of your exercise, the percentage of carbs burned increases, and the percentage of fats burned decreases.

When your heart rate is at 60-70% of your maximum heart rate, we say you are in the Fat Burning Zone. In this range, about 70% of your calories come from fat. To calculate your maximum heart rate subtract your age from 220. This is the maximum safe heart rate. Then to find your fat burning zone, multiply your max heart rate by .65. This will give you a number right in the middle of that 60-70% range.

Percentages vs. Total Calories Burned

Working out in the Fat Burning Zone might sound like a good idea, and it can be! But it’s important to understand that burning a higher percentage of calories from fat doesn’t mean burning more total calories from fat. In fact, if you exercise for the same amount of time, working at in the Fat Burning Zone will actually burn less fat than exercising at a higher intensity.

If you’re not limited by time, working out in the Fat Burning Zone can actually burn more fat. However most people are not going to have two hours to spend exercising.

What the Fat Burning Zone reveals is that low-intensity exercise – things like walking or taking the stairs – done throughout your normal day can be just as beneficial for fat loss as short bursts of activity at the gym. If you want to lose weight quickly, working low-intensity exercise into your daily routine is a great idea.