Why the ‘fat burning zone’ is complete bollocks!

I posted an image a few days ago comparing my heart rate during a workout session after having a pre workout drink to my heart rate during the same workout session without it.

I was actually pretty impressed with the difference. I’ve been struggling with fatigue for a while due to my thyroid function now being underactive due to me being over medicated for Graves’ disease and the BCAA pre-work powder from Bio-synergy really helped me maintain a higher intensity for longer.

But anyway, posting it caused a little bit of confusion for others.

My workout comparison image that caused concern!

I used the application ‘Polar Flow’ and the polar H7 chest strap to track my heart rate during workouts, and one of its very helpful features it to advise you what percentage of calorie expenditure is from fats. It’s a function I ignore and learned means absolutely nothing a long time a go. But the response my post got has kinda demonstrated that people are still under the impression that staying in your ‘fat burning’ zone is optimal for weight loss. Including another local fitness instructor who very kindly messaged to make me aware of my training mistake by wanting to work outside my fat loss zone, so I thought I’d write this in a hope that it will help my students, friends and family realise that the fat burning zone is total tosh.

It is true that at some exercise intensities, the human body burns a higher percentage of fat than it does at other intensities. But that doesn’t mean that staying at that intensity is the key to losing weight. And anyone that believes there is a specific fat melting margin is trying to simplify a very complex process and is ignoring the greater importance of overall calorie expenditure.

Your body mainly fuels itself by burning a mix of carbohydrates and stored fats. Generally speaking, the less active you are, the higher the percentage of that is from fats and as intensity increases the percentage of fuel from fats decreases.

It might seem like it would be much more efficient to be working at a higher fat burning percentage but the theory completely ignores the fact that weight loss or maintaining weight is purely down to total number of calories in Vs calories out. If you put in less calories than you are using then your body is forced to source that fuel from elsewhere, i.e by breaking down the fat in the body. So it doesn’t matter if that fat is burned during exercise or while you’re resting.

If the trick to fat loss was to focus on the percentage of fat used to fuel the body then it would make sense to stay still as that’s when your body is burning the highest percentage of fat compared to carbohydrates but it’s the total number of calories used that matters more!

The general consensus is that the ‘fat burning zone’ is working around 55-65% of your maximum heart rate. The truth is that working at this level will do very little to change your body composition and it will take a lot longer to burn the same number of calories as you would working at a much higher intensity and as people generally planned their work out based on time and not how many calories they want to burn, it is much more efficient to work at a higher intensity for less time.

Weight loss is totally dependent on calories in being less than calories out, and working at a higher intensity makes it much easier to do achieve that.

There is also the afterburn that needs to be taken into account, although people generally over estimate this way to much. But the harder the body is worked, the longer it takes to repair and the faster your metabolism will be while that happens.

My magic juice, it makes me work harder!

So if any fitness instructor or personal training starts telling you that to efficiently lose weight that you need to stay in the ‘fat burning zone’, or someone is selling an exercise class that is designed to focus working in the fat melting margin, then avoid them at all costs. The fat burning zone ideas where debunked years ago so either their training is out of date or they just generally don’t know what they are talking about!

Having said all there, there is definitely a place for lower intensity training sessions. And mixing them in with higher intensity workouts will help with recovery and will help prevent over training. They’re also great for people just getting back into exercise. Just don’t be fooled that they are the key to amazing weight loss.

Published by aerialemma

I'm a 40 year old aerial arts and pole dance instructor who has recently been diagnosed with Graves' Disease

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