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I recently was reading a blog that stirred up some controversy about exercising in the fat-burning zone.  We’ve all heard it before, “When trying to lose weight, it’s best to exercise in the fat-burning zone.”  We’ve also heard that this is a myth, and as a result, it can leave us with our heads spinning over the confusion of what to believe.

Well consider this the end to the confusion, and not just the end to the debate, but reasons for why one school of thinking is right, and why one is wrong.  For those of you trying to lose weight, here it is.  The whole “fat-burning zone is better” concept is a complete myth.

Here’s why.  As I’ve said in the past, when talking about weight loss, it all comes down to a calorie battle.  Calories eaten need to be less than calories burned.  If not, you can kiss your weight loss results goodbye!  Calories out comes from exercise, lifting weights and doing cardiovascular exercise to be more specific.  So doesn’t it make sense that the more calories you burn off from a specific exercise (walking on a treadmill, for example), the faster you’ll lose weight/fat? 

So why do people believe exercising in the fat-burning zone is best?  What is the fat-burning zone?  Good question.  The fat-burning zone is defined as 35-69% of your maximum heart rate.  The best way to find what your heart rate would be in this zone is to follow the simple formula of 220 - age = MHR – RHR x .65 + RHR = 65% of your maximum heart rate.  Huh?  Exactly.  Now in English; wake up in the morning and find your resting heart rate (RHR); feel for your pulse at your left wrist with your right index and middle fingers.  Count the beats for 15 seconds and multiply that number by 4.  This is your resting heart rate.  In the equation, MHR is your maximum heart rate.  You shouldn’t exercise over that heart rate.  For this example, let’s take a 35 year-old person with a resting heart rate of 65. 220 - (35 years old) = 185.  For this person, they shouldn’t exercise over their MHR of 185.  Take 185 - a RHR of 65 = 120.  Take 120 and multiply that by .65 (.65 represents 65% of MHR).  This’ll give you 78.  Add the RHR of 65 back into 78 to get 143.  143 is considered 65% of the MHR for this person.  So to find the fat-burning zone heart rate range of 35-69%, use this formula to give you that range.

Alright, hopefully that equation makes sense.  Now back to what I was saying.  So why do people believe exercising in the fat-burning zone is best?  When you exercise in the fat-burning zone, about 60% of the calories burned off come from fat.  That’s sounds good, right?  Remember though, weight loss is about how many total calories can be burned off, not how many fat calories can be burned off.  A calorie is a calorie.  Any calorie burned off translates into fat being burned off.  As you burn more calories off, the only way for your body to keep its energy level up is to either burn off muscle, or burn off stored fat.  By combining weight training with cardio, you ensure that the muscle that’s burned off is replaced with new muscle from lifting weights.  This leaves the majority of weight loss coming from fat loss and not muscles loss; a very good thing! 

Although 60% of the calories burned off while exercising in the fat-burning zone come from fat, the overall number of calories burned off isn’t very high.  For example, let’s say you do a low-intensity aerobics class for 30 minutes.  This equals about 200 calories burned off during that aerobics class.  Since low intensity can be considered the fat burning zone, about 120 of those calories burned off come from fat.  Let’s say you do that same class at a higher intensity (70-90+% of your MHR) for 30 minutes.  While the percentage of calories that were burned off from fat may be more around 35%, you’re still burning a greater amount of total calories.  In a 30-minute, high-intensity aerobics class, you burn off around 350-400 calories.  Though only 35% of your burned calories are coming from fat, 35% of 400 is still 140!  So not only are you burning more fat calories, you’re also burning more total calories, and that’s the most important thing to remember.

Even though a greater percentage of fat is burned off in the fat-burning zone, overall, more calories are burned off with high-intensity exercise, meaning that even more fat loss will result. 

This doesn’t mean that exercising at a lower intensity is a bad thing.  It just means you’d have to exercise for a lot longer at a lower intensity to achieve the same calorie burn results that come from shorter, higher-intensity cardiovascular exercise.  Plus, when first starting an exercise program, you may only be able to survive a 30-minute, low-intensity cardio workout.  The most important thing to remember is anything is better than nothing, but when it comes to which is better for weight loss, high-intensity exercise is the winner hands down. 

Dan Falkenberg is the co-founder and co-owner of Your Live Trainers.  He can be reached at DanFalkenberg.com.

Tags: cardiovascular exercise, program design, weight loss