The (not so) Magical "Fat Burning Zone"


Fat loss, weight loss, fitness, personal trainer
The Fat Burning Zone has been pushed as the secret for fat loss, but does it really work?


If you've spent any time on modern cardio equipment or in a commercial gym, then you've probably seen something about the "fat-burning zone". This is the specific heart rate range, often seen as 60-75% of max heart rate, in which your body uses mainly fat as the fuel source for producing energy. To most people's surprise, this heart rate range is not super high and usually feels pretty comfortable to stay in. How can that be? Surely the harder you work the more fat you burn, right?


Actually, your body does indeed use more fat for fuel at lower intensities. It has to do with the way in which your body produces ATP (energy). Long story short, the less urgently your body needs energy (lower intensities) the more your body relies on stored fat for fuel. The more urgently your body needs energy (higher intensities), the more it relies on blood glucose, stored glycogen, and other short-term energy providers.


So if you want to lose fat, should you focus on staying in the fat-burning zone?

ABSOLUTELY NOT! The truth is it doesn't matter that much...


On a technicality, yes the fat burning zone does burn more fat. However, this effect only happens acutely at the moment that you are training. What this neglects to take into consideration is what drives fat loss altogether: a negative energy balance or in other words, a calorie deficit. While you are in the fat-burning zone you may be using more fat for fuel, but you also are burning fewer calories since you are working at a lower intensity. As you can see, being in the fat-burning zone is a classic example of winning the battle but losing the war.


Here's an example...


1. Jane is a 20-year-old college student who is a little overweight and wants to drop a few pounds. She does cardio 3 x/wk for 45 minutes and always stays in her fat-burning zone of HR 120-150. She expends roughly 2,600 calories per day on average.


Since she started exercising 4 weeks ago, Jane consumed an average of 2,950 calories per day. Since she started exercising, she has GAINED about 3 lbs.


2. Mary is a 50-year-old working mother who is a little overweight and wants to drop a few pounds. She does cardio 3 x/wk for 45 minutes (in addition to lifting weights...see this later!) but she goes by feel and some days pushes harder than others. She expends roughly 2,300 calories per day on average.


Since she started exercising 4 weeks ago, Mary consumed an average of 1,950 calories per day. Since she started exercising, she has LOST about 3 lbs.


As you can see, it is not enough to simply be in the "fat-burning zone". There is no magic in it that can help you escape the reality of calories in and calories out.


So why do companies always advertise this phenomenon then?