The Magic "Fat Burning Zone"

In every activity you’ll use a combination of CHO (carbohydrates) and fat stores as a source of energy.

You often hear people going on about how they are in their fat burning zone and just burning fat...

This idea that you have a magical zone where you suddenly just burn fat when your heart rate is a certain number is nonsense.

The higher your heart rate, the greater your energy expenditure (calories burnt). If you thrash your car, the engine works harder meaning your use more petrol - same principle applies to your body and the calories it uses for fuel/energy.

Here is two examples:

1. Steady speed sat on a bike: Your heart rate is around 115bpm and after 30 minutes you have burnt 200 Kcals, this is split 60% fat stores and 40% CHO. You used your fat stores for 120 Kcals, figuratively.

2. Same bike but at a higher intensity: Your heart rate is around 150bpm and after 30mins you have burnt 500 Kcals, split 40% fat stores and 60% CHO. You used your fat stores for 200 Kcals, figuratively.

So yes you burn a greater percentage, but not a greater total!!

So why do machines at the gym and some smart watches tell us that we are in a fat burning zone? - Marketing!! If you are unaware of the actual evidence behind it a fat burning zone sounds amazing, right? You would continue to use that machine at the gym or you would continue to use your smart watch. I am a fan of smart watches in general, but this is one thing they should either leave out or explain to consumers instead of shading over the truth.

Smart watch blog: https://www.jetraining.co.uk/post/apple-vs-fitbit

In short, the fat burning zone is not magical and is kind of misleading.

Stay safe,

Josh.