Night Eating (also known as Nocturnal Eating Syndrome) is a condition where people engage in binge eating before they go to bed. They will also awaken during the night and binge eat. It is not considered an official eating disorder, but is up for consideration for inclusion in the next edition of the DSM (Diagnostic and Statistical Manual of Mental Disorders).
What is the relationship to obesity?
In studies, it is estimated that more than 25% of obese people suffer from Night Eating Syndrome. Obviously, if you're getting up 4 or 5 times a night to eat, you're eating more calories than you would if you didn't get up. People who do this eating at night can consume more than half their daily calories overnight.
There seems to be a driving force behind the eating. It is often true that people who eat at night several times throughout the night cannot fall back to sleep without eating.