Fat Burning Zone - What is the Fat Burning Zone?

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First of all, the 'fat burning zone' isn't a true zone.  Or rather it's not the technical name for working at that level of intensity.  And, unfortunately, the name is very misleading because you don't necessarily burn more fat in your so-called fat burning zone.

What is Your Fat Burning Zone?

Wherever that name came from, the fat burning zone refers to the low end of your target heart rate zone, which is about 60-70% of your maximum heart rate.

This is low intensity exercise, around a Level 3-5 on this perceived exertion chart, or the equivalent to taking a walk, a slow bike ride, etc.

This is typically where you want to be during your warm up.

Do You Burn More Fat in the Fat Burning Zone?

Short answer: No.

The longer answer has to do with how the fat burning zone came about.  Experts found that, if you work at a low intensity, your body uses more fuel for fat.  When you work at high intensities, your body uses more carbs for fuel.  Now, people took that to mean that when you use fat for fuel, that you're actually burning more fat.

However, that isn't the case.

The truth is, you'll burn more overall calories if you work at a higher intensity level and, guess what?  Working at high intensities also increases your fat oxidation after your workout, what we call the after burn.

The bottom line is that, if you want to get results, you need to burn more calories and that is very hard to do when you're working at such a low intensity.

When to Use Low Intensity Training

This doesn't mean working in your fat burning zone is a complete waste of time.  The fat burning zone is great for:

  • Beginners - If you're just starting out, working at a high intensity will probably feel miserable and it puts you at risk for injury. Starting out at a lower intensity and gradually increasing it over time is the best way to build endurance, power and cardio fitness.
  • When you're sick or not feeling well - If you have a light cold or some other minor illness, lower intensity exercise (if you exercise at all) is the best way to go.  You won't tax an already stressed immune system and it may make you feel a little better.
  • During long workouts - If you're doing an all day thing like riding a bike or walking, save your energy by keeping things slow.
  • To change up your workouts - Our workouts are based on the F.I.T.T. Principle which stands for the frequency of our workouts, the intensity of our workouts, the time or duration and the type of workout we're doing.  Whenever you hit a plateau or get bored, you want to change at least one of these elements and intensity is one of those.  If you're doing a lot of high intensity exercise, adding in more low intensity work may be just what your body needs to avoid overtraining.

While low intensity exercise can be an important part of any fitness routine, staying in the 'fat burning zone' all the time isn't the best choice if your goal is weight loss.

Working at a variety of intensities each week will help you get the most out of each cardio workouts. 

Too much of anything is never a good idea so look at your intensity when planning your workouts for the week.  Try pushing yourself a little if you normally don't and see how your body responds.  Even just getting a little out of your comfort zone is enough to burn more calories and, hopefully, see more results.

Source:

M. W. (n.d.). Heart Rate Myths. Retrieved February 2, 2016, from http://www.acefitness.org/acefit/fitness-programs-article/2425/ACEFit-workout-advice-and-exercise-tips/.

Phelain JF, Reinke E, Harris MA, et al.  "Postexercise energy expenditure and substrate oxidation in young women resulting from exercise bouts of different intensity." J Am Coll Nutr. 1997 Apr;16(2):140-6.

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