It could be a scene from a horror movie called "Night of the Hungry Zombies." A sleepwalker enters the kitchen, grabs anything within reach -- cookies, crackers, even a dish scouring pad -- and chows down, sometimes taking food back to bed.
Only this is a real life nightmare for 43-year-old Anna Ryan, and one million other Americans. And it has nothing at all to do with hunger.
"There's a compulsion to eat. But it's not a hunger-driven behavior," said Dr. Carlos Schenck, a psychiatrist and an expert in sleep research.
He was one of the first to complete a major study on Sleep Related Eating Disorder (SRED), after spending the past 20 years trying to understand it.
"We've had patients consume cat food sandwiches. They've put coffee grounds, Coca-Cola, and eggshells in a blender and consume it. They eat Elmer's Glue. They chew on chunks of frozen pizza and then try to swallow it. They're like sleeping zombies, just walking around headless. Except that they have a mouth to feed."
Ryan is what doctors call a parasomniac, someone with a sleep disorder that leads to an abnormal event during sleep. These odd behaviors can range from walking to having sex, known as sexsomnia, to acts of aggression and violence, all while asleep.
What may trigger the unusual acts of parasomniacs like Ryan is the shutdown of the brain's frontal lobe during sleep, Schenck said. The frontal lobe is the seat of judgment. Brain scan studies and other research shows that when people doze, their frontal lobe switches off. At the same time, the remainder of the brain may become more active and direct the sleep eater to immediately seek food.
"They can get up, they see their environment," Schenck said. "They know where the kitchen is. But they have no judgment, no inhibition. And that's the problem."
Ryan says she has been a sleepwalker since age 12 and she now believes her sleep eating problem started more than 10 years ago. She never remembers a thing about her nightly forays to the kitchen, which she has learned can occur up to four times a night. She first began suspecting she had a problem when she awoke to strange clues in her home.
"There was food missing. Then I would find wrappers around the house," said Ryan, who lives near Kansas City. "Sometimes I'd find things out of place. I knew I put something somewhere that night, and then the next morning it wasn't there. Diets would work real well, and then all of a sudden, they wouldn't work at all."
Unaware that she had been consuming thousands of calories in her overnight kitchen raids, Ryan was frustrated that no matter how strictly she stuck to her diet by day her fight against weight gain seemed to be a losing battle.
"It's just unbelievable that I could that I could do those things and not remember them," Ryan told ABC News. "There's me and then there's this other person who comes at night. I do things that I don't do during the day, so it's like it's another person."
To help diagnose patients who suffer from sleep eating, doctors often have cameras set up to tape their behavior in sleep labs. The results are typically jarring, not necessarily to the doctors but to the patients themselves.
"Patients who have a sleep behavior disorder such as sleep eating, when they see the tape of themselves, they truly are shocked, saying, 'My God. I didn't realize I was capable of doing this,'" said Schenk.