I recently posted this as a factoid status update on my Facebook wall. Someone from the military confirmed the above claim (it's a true claim by the way) and responded with: "When I was in the army, I often used to run on 4 hours of sleep but never felt sleep deprived or the negative effects of sleep deprivation because I always went to bed at 9 pm". I didn't ask for his age - and I imagine that might have been a factor but something can definitely be said about going to bed early. Plus I'm sure you've experienced the refreshment of waking up after a full night of rest, after having gone to bed earlier than normal.
Besides that, sleep can actually help you stay slim.