Originally Posted by
xfimpg
Now this is interesting because my Polar tells me that at an avg. heart rate of 85%, 30% of my calories are from fat, as opposed to an avg. of 70%, it advises me that 50% of my calories are from fat.
Think of what your Polar is telling you this way. Over a given period of time:
70% of Max HR: 500 calories from fat, 500 other (i.e. 50% from fat)
85% of Max HR: 800 calories from fat, 1850 from other (i.e. 30% from fat)
So at 85% effort, even though the percentage of fat used was only 30%, the amount of fat burned was higher (and you lost a lot more weight overall, too).