The Myth of the Fat Burning Zone

Low Intensity Exercise Burns more fat!

If you’ve ever hopped on a treadmill or elliptical you’ve probably seen it: a screen that tells you when you are in the “fat burning zone” vs. the “cardio zone”. In theory, this means that you should stay at this zone to trick your body into burning more fat than carbs in your workout. Maybe you’ve slowed down the intensity of your workout to keep yourself in that fat burning sweet spot in the hopes of getting rid of some extra pounds or you’ve heard that you need to stay in that range to lose the most fat, but is that really what that means? Do we really have to stick to a low intensity workout to burn fat? Let’s dive a little deeper.

The “fat burning zone” isn’t a myth in and of itself–when doing lower intensity exercise (walking or jogging instead of a full on run or sprints) a greater percentage of fat is pulled from your body as a fuel source. This is because higher intensity exercise requires a faster source of energy and turns to carbs instead. But does a greater percent of fat burned mean a greater amount of fat burned overall? Let’s take a look at the table below:

Type of exercise Total calories expended* Percent contribution from fat* Total fat expended*
Low intensity 100 60% 60 fat kcal
High intensity 500 40% 200 fat kcal
Calorie and fat expenditure (example numbers) (Table from: http://blog.nasm.org/certified-personal-trainer/myths-of-weight-management-you-have-to-exercise-at-a-low-intensity-to-burn-fat/)

 

Looking at these numbers, we can see that a greater percent of fat is used in the low intensity exercise, but a greater amount of calories and fat is actually used up in the high intensity workout over the same amount of time! Crazy, right? So what does that mean for you if you are trying to lose weight?

Low intensity and high intensity workouts both have a place in every exercise plan. It is important to build heart and lung capacity through higher intensity cardio workouts (think running or HIIT workouts) and lower intensity exercise can be better for your joints and muscle growth (such as weight lifting or yoga). There is no way around the fact that we should all be doing both types of exercise, but what these numbers are pointing to is a primary focus on higher intensity exercise if fat loss is your ultimate goal. So get out there and enjoy your yoga, but maybe add a spin class or two while you’re at it ;).

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