Cardio Myth - The "Fat Burning Zone"


I have been to hundreds of gyms. All over the country and even in England. And no matter what gym I am in, I always see the same scene. No matter the time, no matter the weather, every cardio piece will be occupied. Every treadmill, every elliptical and every stair master all taken with people who are busting their butts for 30, 40, 50 minutes, all in hopes they lose the elusive body fat. I hate to break the news to you but it doesn't work. Long term anyways.

But why do gyms pay thousands of dollars for 50-100 pieces of cardio if the activity is all for not? And why do gym patrons get on these machines, like mad men and women, and forget about all the other forms of fitness (lifting weights) the place has to offer? And why does this kind of behavior exist anyway? Where does it stem from?

Answer: it’s on every piece of cardio machinery, "the fat burning zone."

For the purpose of this article, I want to discuss a myth about the "fat burning zone" and why doing aerobics as your sole source of exercise may not get you to the promise land.

Before we dive deep into this step, I want to preface it by saying cardio has its place in everyone's program. To what degree, will depend upon your goals, abilities, and preference. For example, as a trainer, I am on my feet most of the day walking around training clients. I have estimated that I walk anywhere from 2 to 4 miles per day just training clients, depending on the client load. This, by most people's standards, is cardio. The problem with relying solely on this activity is that there is no 24-48 hour calorie burn (excessive post oxygen consumption) that allows for great body fat loss. Lifting heavy things or high intensity training is the only way to create an environment where the body will burn constant calories past the actual workout itself. There is also a myth associated with cardio.

Myths are fun, especially when that myth is prominent. The “Fat Burning Zone” myth has stood the test of time, through several decades and held its own in exercise mythology. To this day, people still believe that maintaining their heart rate in the “fat burning zone” is better than short bursts of interval training. Perhaps this has something to do with every piece of cardio equipment having a fat burn option, thus disallowing yourself to get your heart rate past a certain point.

Let me explain this in more detail. The theory is that if I keep my heart rate at low level (60-65% of max), my body will burn more fat than if I were to run a 15 second sprint. That part is true as you will use fat as the predominant fuel source during your workout. Heart rate and intensity are inversely related to which energy system you use. The lower your heart rate, the more oxygen that is available and when oxygen is available you use fat as fuel. The higher your heart rate goes, the less oxygen you have available, and the more you must rely anaerobic sources (glycogen, glucose, and creatine) to perform the exercise. So the thought is, I will walk on a treadmill for 30 minutes, keep my heart rate low, and burn body fat. The answer is no. You can walk on a treadmill all day if you would like, but it’s not going to change your body composition. For one, your body will adapt very quickly. And two, you are not burning a significant amount of calories needed to burn body fat. Want proof? Take an Olympic marathon runner and put them side by side with an Olympic sprinter. What is the difference? There is lower body fat and more muscle tissue in the sprinter. There is a reason for that.


Research has shown that quick bouts of exercise are more beneficial in cardiovascular health but also in body composition change. Dr. Al Sears, M.D. the Director of The Center for Health and Wellness, who has reversed heart disease in over 15,000 patients, has this to say in his book The Doctor's Heart Cure. "When you exercise for more than about 10 minutes, your heart adapts by becoming more efficient. It achieves this efficiency through downsizing. Long-duration exercise makes the heart, lungs and muscles smaller so that they can go longer with less energy, but there's a trade-off. The cardiovascular system becomes very good at handling a 60-minute jog, but it gives up the ability to provide you with big bursts of energy for short periods. Far from protecting your heart."

There is a place for walking on a treadmill, riding a bike, or hopping on an elliptical. It has its place in most everyone’s program design. For example, someone that trains intensely 3 days out of the week and prefers another 1-2 days of cardio, could perform some steady state cardio to keep from overloading the neuromuscular system.

So what should I do instead of doing long bouts of cardio?

The average person will get on a treadmill and go for 30 minutes. Running or walking for that amount of time can become mundane.  So let’s reduce the amount of time (less is better sometimes) and increase the intensity. Don’t forget to warm up before attempting one of these workouts.


Walk on the treadmill for 5 minutes (pick a speed and incline that feels comfortable)

Hop off and do 10 body weight squats, 5 push-ups, and 10 triceps dips.

Repeat this 4-6 times.


Go as hard and as fast as you can on the row machine for 20 seconds

Slow the pace back down and recover for 60 seconds

Repeat 5-8 times.


Sprint on the treadmill for 20 seconds

Straddle the treadmill, take the speed back down to a walk, and recover for 60 seconds.

Repeat 5-8 times.

As you can see, these subtle tweaks can be applied to any apparatus, implementing a different approach to your old school "cardio" routine, and taking it into a conditioning program. Depending upon your goal, conditioning can be done 1-5 days per week.

These are subtle changes, yet effective ones. Every client that I have implemented these strategies with has seen some type of difference. Try it for yourself.

Yours in Fitness,