Josh Bowen: The Myth of the Fat-Burning Zone

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 keeping their heart rate in the “fat burning zone” is better than short bursts of interval training. Maybe it has to do with every piece of cardio equipment has a fat burn option, thus disallowing you to get your heart rate up past a certain.

Let me explain this in more detail. The theory is 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. You will use fat as the predominant fuel during your workout. Heart rate/intensity are inversely related to which energy system you use. The lower your heart rate the more oxygen is available, when oxygen is available you can 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, 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. Wrong! You can walk on a treadmill all day if you want but that’s not going to change your body composition. For one, your body will adapt very quickly. For two, you are not burning any significant calories needed to burn body fat. Want proof take an Olympic marathon runner and put them side by side with an Olympic sprinter. What difference can you tell? 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 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, this loss makes you more vulnerable to a heart attack.”

Also remember the importance of resistance training and body composition change. Post resistance training workout, your body will burn fat 24-48 hours post workout. This is from the increased oxygen needs of the person. When oxygen is available body fat will be burnt.

Are there places for walking on a tread mill, riding a bike or hoping on an elliptical, absolutely. It has its place in most everyone’s program design. For example someone that trainers intense 3 days out of the week and needs another 1-2 days of cardio, could perform some steady state cardio to keep from overloading the neuromuscular system. However if ultimate body fat loss is your goal, interval training is your best bet. 10 kettlebell swings, 10 pushups, 30 seconds on the battling rope and run on the track for 2 laps; great way to crush your body fat percentage.