Research by Carey (2009) published in the Journal of Strength and Conditioning Research concluded that in order to maximise the fat burning process one is recommended to train at 50% of their maximal heart rate. A great way to achieve this is to raise a treadmill to a 30 degree angle and run for 10-15 mins at moderate pace.
Enter your ‘target zone’ in order to hit your fat burning zone!
Carey, D, G. (2009). Quantifying differences in the "fat burning" zone and the aerobic zone: implications for training. Journal of strength and conditioning research. 23(7): 2090-5.