No.
That's a bunch of bullshit, if I'm being blunt.
There's this myth that one must be in the 'fat burning' heart rate zone or workout intensity to realize the best/most fat loss. It simply isn't the case.
To explain where the myth comes from, we have to delve into bioenergetics a bit. That's simply a fancy way of saying how our body fuels various activities. There are 3 primary fuel systems our body uses:
1. oxidative
2. glycolytic
3. phosphocreatine
If we think of it as a spectrum, at lower intensities the oxidative system is used primarily and at high intensities the phosphocreatine system is used primarily. Then there's a lot of middle area where the glycolytic system primarily fuels activity.
At the lower intensities where the oxidative system is primarily used, the actual fuel substrate that is predominantly 'oxidized' or burned is fatty acids... the stuff that resides in your fat cells.
So here the myth is born where lower intensities work best at burning fat.
The problem is, that's not the overriding factor that determines total fat oxidation. What is the overriding factor is net energy balance.
To put it as clearly as possible, you could exercise at a low intensity where the primary source fuel being used is fat and expend 100 calories for example of your could exercise at a higher intensity where the glycolytic and phophocreatine system is primarily fueling the activity (glucose, glycogen and phosphogen ... not fat) and expend 300 calories.
In the latter case, sure, you're burning less fat while exercising than the former case. However, at the end of the day your tapping into more of your fat b/c you created a greater net energy shortage with the more calorically expensive, higher intensity exercise.
I'm winging this b/c I'm about to eat dinner... if you want to read an excellent article on this you can check out .
