To further investigate the workings of their sleepeating, Sherri and Angela agree to undergo a study at Northwestern Memorial Hospital's Sleep Disorders Center.

While she was asleep, research cameras caught Sherri tucking into a midnight snack of milk and corn chips. She moved on to cheese and pepperoni at 12:30 a.m., and then downed mixed nuts at 4 a.m.

Dr. Schenck says Sherri's experiences in these three periods of sleepeating were common—in each, she left medium deep sleep and was not really conscious of her actions. "Sometimes, people have fragments of memories of what they did," he says. "Otherwise, they don't have any memories."

"These folks are not crazy," Dr. Oz says. "They do crazy things, but they're not crazy at all. The brain has lost that ability to control what's going on, so you start to act out in ways you normally wouldn't."