Weight / Fat loss

Doing proper exercise was too hard so when someone said "oh, look you burn a higher % of fat if you just walk to 60% HRmax" they were all like woo hoo and all the fat burning zone books appeared.

"burn a higher % of fat" was the big bit they all misunderstood and ran off in the wrong direction with, e.g. if (made up numbers) at:-

• lower intensity you burn 100kcal/hr from fat and 100kcal/hr from carbs
  
• a higher intensity you burn 120kcal/hr from fat and 130kcal/hr from carbs
  
  

then lower intensity is not "better" just because you get 50% of energy from burning fat compared to 48% at higher intensity. With these made up figures you burn more fat at the higher intensity, not where the best percentage lies.

But if at lower intensity you burn x fat and y carbs and then at a higher intensity you burn the same amount of fat (x) but 1.5y carbs then there's no huge benefit looking at just the session alone (post exercise effects are another matter) since you end up burning the same amount of fat either way.

(Further effects would be that the higher intensity session should improve your overall CV fitness more, barring overtraining, so that you'll probably be even more efficient for future sessions which could lead to more fat burn, etc. It's going to be very complex.)

What would be useful is if someone has done a study to see at what rate fat and carbs are burned at different exercise intensities.

If fat burn increases slightly at higher intensities then all the better to go out and smash it, but if the body starts to burn less fat (and more and more carbs) at higher intensities then smashing it might not be so beneficial.

No idea how they'd actually measure that though, probably #magnets