I recently experienced a small victory in my budding career as a blogger: I had my first spam comment. The comment was promoting a specialized workout program that made use of the so-called "fat loss zone" and stated that many people are actually working out too hard and that your exercising could be counterproductive. I had heard this theory before. Indeed, if you've ever used a treadmill, you've probably been exposed to it in the form of those little "heart rate zone" charts. But I have never experienced it myself, even when training for a race and knew little of the science behind it. So I decided to investigate.
What is the Fat Loss Zone?
The fat loss zone refers to a range of heart rate achieved during low-intensity cardiovascular exercise that supposedly helps you burn fat more efficiently. Proponents go even further and state that if you workout too hard, bringing your heart rate above this zone, your body will start to burn muscle for fuel.
Is it True?
To a point, yes. It is true in that the fat loss zone exists. It is false,however, in that it has been misinterpreted. Despite what people say, the body does not burn a higher amount of fat in this zone but it burns a higher percentage of fat. Your body is constantly using a blend of fat and carbohydrates as fuel in varying amounts depending on its immediate demands. According to the endurance sports experts over at Active.com "At lower intensities the body may burn 50 percent of the calories from fat, while at higher intensities it may only burn 35 percent. But at higher intensities you burn way more total calories—and more fat calories overall—than you do at lower intensities."
Does the Body Burn Muscle for Fuel at High-Intensities?
No. The only time your body turns on muscle reserves for fuel is during crash or starvation diets. Muscle is very important to literally everything you do and your body doesn't want to give it up. A study published in the American Journal of Clinical Nutrition tested the effect of exercise intensity on both muscle and fat loss and found no correlation.
Is it Possible to Workout Too Hard?
Of course it is. But not because it makes you lose muscle. It's possible to workout too hard because you can hurt yourself through overuse and other injuries. Consult your doctor or other healthcare provider before beginning any exercise routine and listen to your body while figuring out which intensity works for you.
Bodybuilding legend and prolific writer Clarence Bass wrote an excellent and well-researched article on this topic that I highly recommend if you would like more information.
