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?
That's easy! They do it to exploit you, prey on your fears, and make a profit from it. People would much rather believe that losing weight is as easy as keeping their heart rate between two specific numbers than face the reality that it is a very simple but very frustrating process.
Okay, so what SHOULD I focus on?...
To lose weight, you need to keep things simple and focused. Don't waste time and energy thinking about the tiniest details like fat burning zones, ketogenic diets, or any other hyper-specific regimen. Here is what the science supports for sustained, life-long body transformation:
1. Consume fewer calories than you expend. This is the big one and there's no way around it. If you are struggling to lose weight, there is a great chance you consume more calories than you realize. The little things like oils, sauces, dips, dressings, etc...they really add up.
2. Prioritize resistance training. Cardio is very important for your heart, but it has little to do with weight loss other than being a means of burning calories. Resistance training offers functional, aesthetic, and cardiovascular benefits all while actually increasing how many calories your body burns at rest. To get more bang-for-your-buck, resistance training is the way to go, with some cardio at the end to keep your heart strong.
3. Bump up the protein (but don't demonize other nutrients). Increasing your protein intake will help keep you feeling full throughout the day and help with building some muscle. In turn, this increases the number of calories you burn at rest which helps you with fat loss. When planning your meals think about your protein source first, then plan everything else around that.
**By the way, carbs are not your enemy. Do not let fear of this nutrient guide your food choices. Carbohydrate is an important nutrient that our bodies are designed to consume and break down. You can absolutely eat carbs, lose weight, and keep it off for the rest of your life.
To summarize...
That fat-burning zone has been widely popularized and exploited by gyms, but there is nothing special about it and it is not worth your time to focus on. Instead, focus on the time-tested and science-backed methods that have led to the consistent success of millions over the years. Make sure you are in a calorie deficit, start strength training, and try to get your protein up a bit.
If you have any questions about losing weight, don't hesitate to ask. At Anderson Sport & Fitness, we specialize in keeping weight loss simple and effective for our clients so that they can maintain it for their entire life. Drop us a line! Hope to hear from you soon...