Why the Fat Burning Zone is Nonsense9 min estimated reading time

fat burning zone heart rate


Why The Ideal Heart Rate for The Fat Burning Zone Does Not Exist


There are a series of stubborn myths in the fitness world. Today I discuss the myth around the ‘ideal’ heartbeat for maximum fat burning, also known as the fat burning zone.

The myth is that if you sport in the right heart rate zone you burn the highest percentage of fat compared to the total number of calories.

That sounds good, probably because the media sometimes uses it. Yet this theory is somewhat misleading. In this article, look at what scientific research says about the fat burning zone.

What you will learn in this article:

  • Why the ideal heart rate is misleading
  • How to burn more fat and calories (in less time)
  • How you can benefit from the after-burn effect

If you look at the older fitness equipment, you sometimes see pictures explaining the fat burning zone. burning zone-cardio

Here is such a picture:

Burning Cardio Zone

In the yellow zone (maximum fat burn zone), your percentage of weight would burn the most fat.

To get into this zone, you should train at around 60% to 70% of your maximum heart rate.

How do You Calculate The Ideal Heart Rate?

In order to calculate the ideal heart rate, you first need to calculate your maximum heart rate.

The formula is as follows:

220 – current age = maximum heart rate

Suppose you are 40, then the calculation is: 220 – 40 = 180 MHR (max heart rate).

For the maximum fat burning, you would then have to sit between 60 and 70% of this heart rate.

That will be:

  • Lower heart rate zone limit: 60% of 180 = 108 bpm
  • Upper heart rate zone limit: 70% of 180 = 126 bpm

In short, the ideal heart rate zone should be between 108 and 126 in this example. In this zone, according to the theory, there would, therefore, be maximum fat burning.

Another common way to calculate your maximum heart rate is 206.9 – (0.67 * age).

Training Less Hard with More Results?

Many old fitness theories have since been disproved, but one that can still be read on many old cardio machines, is the alleged power of the ‘fat burning zone’, that is to say, that with a moderate intensity of a person’s maximum heart rate the optimal level for fat burning is accomplished.

But the fat burning process of our body is much more complex than that. Although the percentage of fat burning may be higher, the total number of calories you burn is less than what would happen if you exercise at a higher intensity.

The theory suggests that you should not train on your maximum heart rate, because at a heart rate of 60-70% you would still burn more fat.

The inattentive people will take this theory for granted, but if you just look further than your nose is long, you will see that it is not quite right.

It is true that you burn more fat percentage-wise, but it is the same as the total fat burning …

We can make that clear with the following example:

Imagine you win a gold bar and you can choose between the following two bars:

  • 1 kilo of 24-carat gold bar (99.9% content) worth $ 40,000
  • 2 kilos of 18-carat gold bar (75% content) worth $ 60,000

Which do you choose? Do you go for the gold bar that has the highest gold content 99.9% or chooses the one that has the most TOTAL value?

Of course, most people choose the gold bar with the highest value. The same principle applies to the fat burning zone. This zone gives you the most fat burning percentage. However, this does not mean that the total fat loss is higher.

Why you do Not Burn Maximum Fat in the Fat Burning Zone

If the ideal heart rate for the fat burning zone is nonsense, you may wonder what is the best way to burn fat.

To tell that I will first have to give some explanation about some terms. Then I will show you a table where you can see exactly that a higher heart rate causes more fat burning!

We start with the terms …. your body basically has two sources for the energy supply, namely fats and glycogen. Glycogen is a glucose supply in your liver and muscles that were originally glucose and gets you out of carbohydrates. For convenience, you can call glycogen a sugar supply in your body.

So if your sport burns your fats and glycogen, but in what proportion? Well, that has to do with the intensity.

The calculation that refutes the theory

  • If you train at 65% of your heart rate (fat burning zone), the burning ratio is around 40% fat and 60% glycogen.
  • On the contrary, if you train at 85% of your heart rate, the ratio is approximately 35% fat and 65% glycogen (source, source, source).

* Since the studies use VO2max instead of MHR I used the formula% MHR = 0.6463 x% VO2max + 37.182 to convert the values.

If you set your sport for 30 minutes, you will burn approximately the following number of calories:

  • 300 calories when you train at 65% of your heart rate *
  • 500 calories when you train at 85% of your heart rate *

* Of course, the number of calories you burn depends on your body characteristics.
The following table shows how many fats, glycogen (sugar supply) and calories you burn completely when you train for 30 minutes on different types of intensity.

30 minutes of trainingFat BurningGlycogen burningTotal calories
Fat burning zone (65%)120 kcal180 kcal300 kcal
High intensity (85%)175 kcal325 kcal500 kcal

As you can see in the table, you burn more fat at a high intensity than at the low intensity, despite the fact that you burn more fat in the low intensity.

In the example, you burn 46% more fat calories in the high-intensity variant.

Why you actually Burn more Fats in High Intensity

When people think about burning calories, they are always talking about burning during exercise.

But did you also know that:

  • You burn calories at rest
  • You burn more calories after a workout at rest than if you had not trained

That after you burn more calories than you would normally do when you are at rest, we also call the afterburn effect. Officially this is called the excess post-exercise oxygen consumption, abbreviated EPOC (source).

How Big is The Afterburn Effect?

A study from 2005 investigated the afterburn effect (source). In the study, participants were assigned to two groups. In one group, participants cycled at a constant pace for 3.5 minutes. In the other group, participants were asked to do 3 sprints of 15 seconds each as quickly as possible.

This is what the groups burned during the sporting activity:

  • Cycling group: an average of 29 calories per participant
  • Sprint group: an average of 4 calories per participant

Yet the burned calories were completely different after the training. Here they are:

  • Cycling group: an average of 39 calories per participant
  • Sprint group: an average of 65 calories per participant

Weird huh? So big is the afterburn effect:

  • Cycling group: 26% of the total calorie combustion!
  • Sprint group: 94% of the total calorie combustion!

That’s what you hear … 94% afterburn effect!

From another study (source) with a longer sports duration showed that with an intensive spinning training of 45 minutes you burn more calories for no less than 14 hours.

In the 45-minute training, the participants had burned an average of 519 calories, adding an additional 190 calories after 14 hours. In short, the afterburn effect increases the number of calories burned by nearly 37%! Other studies show lower numbers (source, source).

Strength training has shown that the afterburn effect can last up to 38 hours (source).

I think you understand the message … the afterburn effect is not negligible and it is many times higher with high-intensity training. (HIIT)

In short, you know what to do if you want to burn fat! Although … nutrition is still the most important if you want to lose fat and want to be slimmer. Based on research ( source) and practical experience, the impact of food is about 80% compared to 20% sport.

Frequently asked questions about the Fat Burning Zone and Heart Rate Zones

Question 1: Is training at low intensity a waste of your time?

No, not so much because you still burn calories and exercise is healthy! But if you want to burn fat optimally, you can better exercise at high intensity.

Question 2: Can I / should I immediately start exercising at high intensity?

Yes, that is difficult. If you want to burn fat in a short period of time, you can better train at high intensity.

But if you are a beginner, this may be too challenging. Start quietly and build it up. With that idea in mind, you can also start cardio at low intensity first.

The following weeks you will continue to increase it.

Question 3: Can I also exercise for a longer time (eg 60 min) at low intensity so that I can keep up? Will I no longer burn fat in the end?

You can indeed do that. A disadvantage is that you lose muscle mass if you start running for so long. Muscle mass (also for women!) Provides a sexy figure instead of being lean.

So you can certainly do it, but then you do it more for fun and your health than you really burn fat with it.

Question 4: Can you train on more than 85% of your heart rate (zone)?

That depends on how fit you are and your age. A young top athlete can achieve up to 95% of his maximum heart rate with a super fanatical workout.

If you have little experience and you are elderly, a heart rate of 85% is not recommended. It can lead to dizziness and other more fatal consequences.

If you are worried about your maximum heart rate, use a heart rate monitor and discover how far you can go.

Question 5: Is it wise to do a long training at high intensity?

You could do that, but that is generally not recommended. With a longer training session, you will go anti at a given time! create stress hormone cortisol.

The cortisol hormone causes you to hold fat faster.

Overtraining can also have harmful effects on the immune system (source). Training with a high intensity of up to 30 minutes is more than sufficient (source).

Remember that taking a rest is just as important as training yourself (source).

A Good Way to Burn Fat and Calories

Do you want to lose fat, maintain muscle mass and burn most calories in proportion? Then go for interval training! Research shows that a high intensity alternates with short breaks for most fat burning causes (source). This is because all kinds of muscle fibers are used and take full advantage of the afterburn effect.

That does not mean that every workout you do must have a high intensity – this can lead to injuries and physical fatigue – but they also do not all have to have a moderate intensity, especially if weight loss is your ultimate goal.

Did you know that research shows that 1 in 3 just gains from a diet instead of losing weight? (source)

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