one thing i would like to put into this is your burn fat and calories at two completely different levels. to burn fat you need to have raised your heart rate slightly but not to the point were your gasping for air. also you need to do this for a little while. say 30 -45 minutes of fast walking with your treadmill at an incline will do the trick. if its calories you want to burn this is when you need to start looking at running and interval training. many people that are overweight will only need to burn fat until they get down to a healthier level where they can train harder.
also it may be best to train in the morning but dont get to caught up with that. training anytime of the day is better than not training at all. also as others have mentioned diet is very inportant. there is no point training if your filling yourself full of rubbish. i personally rink lots of water and stick to 1200 calories a day but you need to find what works for you.