In order to burn fat aerobically, remember to use the ABCs of supplements. They are:
A=Alpha Lipoic Acid
B=Vitamins B1, B2, B3
C=L-Carnatine, CoQ10, Chromium
When exercising, keep your heart rate around 180bpm minus your age to stay in the aerobic zone. Heart rate monitors are great for this. I use a Polar brand to train with.