Burn Fat While You Sleep

Your bedroom should be as dark as possible, because the production of the sleep-promoting hormone Melatonin is stopped immediately, if bright light falls in the eye.
At night melatonin is produced to help our bodies regulate our sleep-wake cycles. The amount of it produced by our body seems to lessen as we get older. Scientists believe this may be why young people have less problem sleeping than older people.

If you sleep less than 7 hours per night you'll block the production of the growth hormone and that will cause you to gain weight.

If you do not get enough sleep, leptin levels will go down and you will feel more hungry and you will eat more next day.
As you can see if you do not get enough sleep, your body will not produce hormones that you need to burn fat.