What does it mean to be in the fat burning zone?
What Is The “Fat Burning Zone”?
Does the fat burning zone exist – what is it and how does it work?
Is the fat burning zone a marketing myth?
If you have ever set foot on a treadmill or cross trainer, you will know about the fat burning zone.
Every gym machine tells you about it: that band of heart rate BPM between low level exercise and high intensity training.
But what nobody ever seems to explain is what the fat burning zone is?
Why is this middle ground of heart rate so good for burning fat? And what does the body burn at lower and higher level cardio?
Calculate Your Fat Burning Zone
Here is the theory on how to calculate your personal fat burning zone by heart rate.
220 minute your age = your max heart rate (MHR)
MHR multiplied by 0.6 = low end of your fat burning zone
MHR multiplied by 0.75 = high end of your fat burning zone
As an example: if you are 30, then your fat burning zone is between 114-142 bpm.
Bear in mind, that is a pretty big range (for most healthy 30 year old people, walking fast would get their heart rate above 114, but stepping fast on a stair master would barely get them to a sustained 142 bpm).
Fat Burning Zone and Heart Rate
The theory of the fat burning zone says that if you train within your personal version of this range, you burn more fat (as a percentage of calories burned).
Is The Fat Burning Zone A Myth?
Well, yes and no.
Yes, there is a heart rate zone at which you can probably sustain more effective cardio than any other.
Using our example above, the person could probably do cardio at less than 114 for ages, but just imagine how undemanding it would be!
And they could certainly train at over 142 bpm, but it is unlikely they could sustain it for even a few minutes.
So the zone of 114-142 bpm (in their personal calculation) is a great balance: hard enough to be worth it, but not so intense that they can not sustain it.
But there’s something about the fat burning zone you need to understand.
When we do high intensity exercise, we use more carbohydrate for energy.
And when we do lower intensity exercise, we use more of a percentage of fat for fuel.
That is where the idea of the fat burning zone comes in.
And when do we have the lowest heart rate of all? When we are tucked up away in bed asleep.
Fat is a great source of energy, so your body relies primarily on it when you are at rest.
However, this changes once you start to move more quickly.
Your body turns to carbs (because fat isn’t a quick enough fuel source to cope with immediate energy demands).
Carbohydrates don not provide as much energy, but they provide it more quickly than fats do.
Once you go back to low level activity or total rest, your body can rely on its favorite fuel source – fat – again.
So actually – no joke – the best fat burning zone is when you are at rest.
This is when you burn the largest amount of fat – as a percentage of energy used.
But if you are reading this, you don not want to go to bed early just to burn more body fat.
You want to know the best form of cardio for getting lean.
The Best Exercise To Burn Fat
So we have established that low level exercise burns the largest amount of fat for fuel (as a percentage of total fuel burned).
Yet higher intensity exercise burns more calories over all. Therefore, the best exercise to burn fat is the type that you enjoy and will do most often.
[Quantifying differences in the “fat burning” zone and the aerobic zone: implications for training. Carey DG. J Strength Cond Res. 2009 Oct;23(7):2090-5. doi: 10.1519/JSC.0b013e3181bac5c5.]
If you have time to do a significant amount of low level cardio (30-60 minutes) often enough to burn the calories you need to burn, then do it.
You will be in your fat burning zone, and you will be using mostly fat as fuel.
However, if you don not have the time, or if you prefer your cardio to be hard and intense, then do HIIT or intervals.
Sure, you will burn more glucose as fuel, but you will still burn fat and you will definitely torch calories.
However you choose to burn your fat, try to vary your exercise across the week.
Don not do all HIIT, or all low level cardio.
Different forms of exercise benefit you in different ways: fitness, strength, power, and endurance.
Aim for a healthy heart as well as impressive muscle mass, and your body will tend to carry less over all fat anyway.
Remember that a calorie deficit is the absolute fundamental key to losing body fat – however you choose to achieve the deficit!
Is the Fat Burning Zone Legit?
Yes, it is.
There is a heart rate zone at which we burn more fat than carbohydrate for fuel.
But we are all constantly burning fat and expending calories, 24/7 around the clock, whether we are at the gym, out running, or fast asleep.
If you take your entire day into account, you will see that you burn the majority of your calories when you are at rest.
And the more muscle you have on your body, the more calories you’ll get through, all day long.
So what is the best fat burning workout?
It’s adding more muscle!
Then expend any extra energy whichever way you want: whether that’s HIIT, a workout class, a long walk, or 30 minutes of Netflix on the treadmill.
Nicola Joyce (aka “the fit writer”) is a fitness industry copywriter who has been writing for and about sport and fitness since 2004. Nicola is a competitive drug-free bodybuilder (with two World titles at amateur level) and has also competed in powerlifting and a couple of strongman comps. Prior to her strength training days, Nicola was an endurance athlete and has even swum the English Channel twice. She can be found on all social media at: thefitwriter.