umm..
anaerobic levels a ctually burn mostly glycogen that is stored in your liver or muscles, because your body doesnt have time to oxidize fat (aerobics) YOu can pretty quickly deplette your glycogen stores, however.
ALso, regarding HR monitor...if you used the standard formula for Max HR, than you may not be working as high as you think you are.... that 220 minus age, or whatever.... it doesnt work like that.... its more like a starting point, like a BMR online calculator.
Also, if youre working anaerobic, than you are technically burning more TOTAL calories, and therefore, at the end of the day, end up burning more fat.
Just move