Blasting the Fat Burning Zone Misconception

Youniverse Contributor Heather Gannoe, ACSM EP-C

In the fitness world, it can be hard to differentiate fact from fiction. We are bombarded with infomercials promising us rock hard abs by simply popping a diet pill or wearing a belt that will zap our core into shape.  Books and videos tell us to “eat this, not that”, or that we only have to exercise for 10 minutes a day for a svelte beach body. We also know that a vast portion of our society is, unfortunately, still holding out for a “quick fix” to weight loss. Combine these factors together, and we have an industry that is constantly one upping itself with the latest/greatest/fastest way to (supposedly) lose weight … until it’s proven that this doesn’t work and everyone moves on to the next trend.

Needless to say, it’s no wonder so many people are utterly confused when it comes to fitness.

But all gimmicks and “quick fixes” aside, there are still proven facts and methods that while based on science, have been misconstrued over time by misinformed fitness seekers.  These topics can be and unfortunately are often misrepresented as something that isn’t exactly what you think it is.

Case in point: the “fat burning zone”.

It’s often plastered all over the screens of cardio equipment. When your heart rate is in the green area you are in the “fat burning zone”. Sounds great, right? Shedding fat is the ultimate goal of so many exercisers.  Yet I often see gym members and clients slaving away on said equipment, bored to tears, not working as hard as they think they should be (but the machine says fat burning!), and still not seeing results. And the reason is because the “fat burning zone”, while accurate in description, is misleading in outcome when referring to weight loss.

This is not groundbreaking news, in fact it has been explained across the internet time and time again. Though many do refer to the “fat burning zone” as a myth, I have to disagree, it is simply a misunderstanding.  So let’s explain the fat burning zone in easier to understand terms:

Just like a car, your body needs fuel in order to work. Its two main fuel sources during exercise are fat and carbohydrates.  One gram of fat contains 9 calories. One gram of carbohydrate contains 4 calories. Calories are energy, or the “fuel” for your body.

The “Fat Burning Zone” generally occurs at about 60-70% of your maximum heart rate. This is what most would consider lower to moderate intensity exercise.  Imagine a brisk walk that causes your breathing and heart rate to increase, but nothing overly strenuous; you could still carry on a conversation if necessary.  In this zone you are utilizing mainly (but not all) fat as a fuel source over carbohydrates.

As mentioned above, fat contains over twice as many calories per gram as carbohydrates. Thus, it is slower burning, as it takes longer to convert to fuel, and requires oxygen to carry out this process (aerobic metabolism). Endurance athletes strive to stay in the fat burning zone, because it takes a lot longer to burn through fat energy stores than carbohydrate stores (namely, glycogen in the blood stream).  Thus athletes in the fat burning zone can run significantly longer, and avoid fatigue longer.

Now, the anaerobic zone generally occurs at about 70-90% of your maximum heart rate. This is what most would consider high intensity exercise.  Picture a solid running or cycling pace that causes you to breathe heavy conversation is difficult.  Here you are utilizing mainly (but again, not all) carbohydrates as a fuel source.

As mentioned above, carbohydrates contain about half the number of calories per gram as fat. This fuel source doesn’t last as long, and there is a whole slew of other physical things that happen when you go “anaerobic” (that we won’t dive into in this post), but the main point is that we burn though carbohydrates faster.

Now I know what you are thinking: “but with twice as many calories to burn!“, “I want to burn fat, that’s why I’m on this blasted elliptical!“, etc. But here’s where it gets tricky… so hold on and stick with me. Remember now, carbohydrates burn FASTER as a fuel than fats. Further, using a bunch of equations that I’m not going to bore/confuse you with, we know that the higher the heart rate, the greater the TOTAL caloric expenditure, regardless of where those calories are coming from.

For example: let’s take a 130 lb female. At 60-65% of maximum heart rate (or, the Fat Burning Zone), she would burn 4.86 calories per minute, 2.43 of those calories from fat. Therefore, 50% of the calories burned are coming from fat.   At 80-85% of maximum heart rate, she would burn 6.86 calories per minute, 2.7 of those calories from fat.  Therefore, 39.85% of the calories burned are coming from fat.


Numbers are purely an example, and vary based on weight, gender, age, actual maximum heart rate, etc.

Over 30 minutes, MORE total calories, as well as more total calories from fat, are burned in the higher intensity zone than the “fat burning zone”. And how do we lose weight? We burn more calories than we consume.. 3500 calories per one single pound to be exact. So in the matter of weight loss, does it really make a difference where those calories come from? Or would you rather your workout be more time efficient?

My suggestion:  ditch the “fat burning zone” mentality (unless of course, you are zone training for specific endurance reasons. That is another topic for another day). Mix up your weekly workouts to contain days of high intensity exercise, days of low intensity exercise (recovery is important), and days that combine intervals of both high and low intensity exercises, such as the 30-minute Express Circuit workout or a group exercise class at your Youfit Health Club.  Don’t forget to incorporate strength training, as increased lean muscle mass will help you burn more calories no matter what you are doing.   Most of all, find something you enjoy doing, and move your body!