By: Chere Lucett NASM-CPT, PES, CES
Chances are we have all fallen victim to some misguided information in health and fitness. With good intentions, much of the mis-information has been handed down from earlier generations of fitness professionals, when research had not caught up with the industry and ideas about fitness were generated by the “it works for me” principle. However today, researchers have been working non-stop to dispell myths and uncover the truth behind common misconceptions. While many concepts have been misunderstood, there are three commonly questioned ideas still lurking in the industry. In no particular order, these misunderstood concepts are the elusive “fat burning” zone, spot training, and enhanced muscle development.
Myth #1 – Fat burning zone
Fat burning has been the number one goal in health clubs around the nation. Given the epidemic of obesity, many people are looking for the golden ticket to fat loss and hence the allure of a “fat burning” cardio zone has shot through the industry like a bullet. While many claim the fat burning zone to be where people burn fat – there is much more to this zone than fat burning and alone, it will not produce the desired results of fat loss if not understood properly.
The “fat burning” zone is defined by a zone of intensity, measured by heart rate, where the body utilizes fat as a high source of fuel. However, it is not the only zone where fat is burned and it is not the only fuel source used. At approximately 40-50% of heart rate max, about 85% of fuel in this zone comes from fat, and roughly 15% of fuel comes from carbohydrates. As the heart rate moves to 60-70% of maximum, the fat burning zone fuel sources change slightly to approximately 75% of fuel from fat, and 25% of fuel from carbohydrates (glycogen).(1) As the heart rate increases, fat utilization decreases and carbohydrate utilization increases. While the lower heart rate zone may create some allure because people want to burn fat, the bottom line lies in the fact that overall caloric burn will determine successful weight loss.
The total amount of calories burned in a session (burn rate) will determine successful fat loss overall. For example, an exerciser working for 30 minutes in a fat burning zone may only burn 100 calories, with 75 of those calories coming from fat as a fuel – creating a more efficicent fat burning machine which is good; however, that same exerciser working at a higher heart rate for 30 minutes may burn 300 calories with only 30 of those calories burned coming from fat (based on higher percentage of carbohydrates used for fuel and decreased percentage of fat utilization for fuel).
Remember that weight loss follows the Laws of Thermodynamics, which loosely translated means that less calories in and more calories out will result in weight loss.(2) Given this, why work in the fat burning zone – does it make a difference? The truth is that while it is misleading to assume that the fat burning zone is better to burn fat because of the higher percentage of fat being utilized, it is a great zone to work on increasing aerobic base (pushing your anaerobic threshold up into a higher heart rate range – enlarging the fat burning range), decreasing the occurance of overtraining and limiting injury during cardiovascular training. It is important to remember that oxygen and glycogen must be present to burn fat and lower heart rate zones allow for larger amounts of oxygen to be exchanged. The larger the aerobic zone – the more fit you are cardiovascularly- the higher amount of calories can be burned (you are working harder), while utilizing fat efficiently as a fuel source.
Essentially, the body learns to work smarter, not harder. But always remember, it is the total overall calories during the training session that count when looking to lose fat. That is the truth and the importance behind the “fat burning” zone.