The other responding mothers are right that you should consider if your son is doing this willfully, or if he has a condition. I also saw a special on "sleep eating". I would talk to your pediatrician about it. Maybe it would be a good idea to set up a video in the kitchen, (which is what I saw them do on the show) and let your doctor see it. If he is doing it conciously, then consider just locking up the kitchen at night and trying to be more strict about him eating his meals and snacks in the daytime.
Also, if he is waking up because he is hungry, maybe a before bedtime snack would hold him over, like milk and peanutbutter crackers, or something else healthy for him.
Good luck
Also - you did not mention how old your son is, or what kind of food schedule you are on.