The "Fat Burning Heart Rate Zone" (muscles, lose fat, lifting weights)

[AndyPettitteIsGreat]

So, I have been reading about the "Fat Burning Heart Rate Zone" - at ~65%-70% of Max Heart rate is where the highest percentage of calories burned are fats (85%).

My question is: Where do the other 15% of calories burned come from - protein or carbohydrates? Also, is it best to do a fat burning workout on an empty stomach?

I want to burn fat (right now at 20% body fat) but do not want to give up any muscle I've put on over the past 6 months. Thanks!

[sportsgeek20]

Well basicly what most more recent studdies show is that
a) muscles are not burned to as high degree outside the "target HR" as previously thought and
b) HIIT is more efficient for burning fat, look it up on wikipedia, might be something for you.

The other 15~% mostly come from carbs.

What is critical is that you continue lifting heavy. This will stimulate your body to keep the muscle.

One thing to count on is that when/if you go below 15%BF things start getting tough.

[Croye22]

OP, I wouldn't advise it. Running on an empty stomach would be pretty bad idea. Best to eat a little something for energy.

Except 1. Lifting weights and doing hiit is counterproductive. People say do it, but saying it is easy. Doing it is NOT. I guarantee you will not be able to lift weights and do hiit without stressing the body even more. hiit will require those days to recover so yeah, lay off the weights if you're trying to lose fat. Worry about muscle later.

And 2. You'll burn calories doing hiit, yes, but the best effect occurs AFTER a HIIT session which can last up to 24 hours. So you'll burn more fat on hiit than regular running.