When you sleep poorly or don't sleep at all, your appetite increases - or so the research indicates.
"New research from Uppsala University, Sweden, shows that a specific brain region that contributes to a person's appetite sensation is more activated in response to food images after one night of sleep loss than after one night of normal sleep." -
source The Source is the Sleep Foundation website, which is a great source for info on improving your sleep habits or determining if you might have a sleeping disorder.