For more than 20 years, he ate three or four times between midnight and 4 a.m. "It took on a life of its own, and my body started waking me up for the food," says Porreca, now 62, a computer manager in Philadelphia. One night he even cooked himself a steak.

He put on 50 pounds before he was diagnosed with a disorder called night eating syndrome.

Like Porreca, people who have this condition consume a third or more of their daily calories after dinner, either before going to bed or during the night, says psychologist Kelly Allison of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine in Philadelphia. They aren't sleepwalking; they're aware of what they're doing. "But there is a feeling of compulsion and anxiety associated with it."

She and her colleagues are presenting new research on the syndrome today in Las Vegas at the annual meeting of the North American Association for the Study of Obesity, a conference being held in partnership with the American Diabetes Association. They've found that the antidepressant Zoloft is effective in controlling night eating, and Allison also has explored treating it with behavior modification strategies.

After enrolling in a university study, Porreca started taking Zoloft. "Within two weeks, I was sleeping through the night." He also lost 25 pounds and his cholesterol dropped. Then he started walking and doing other physical activities, eating healthier and quit smoking.

"I can't believe how well I feel. I didn't realize how wonderful it is to sleep through the night. I feel peppier. I feel tremendous."

Allison has written a new book, "Overcoming Night Eating Syndrome," with Sara Thier and Albert Stunkard, a University of Pennsylvania psychiatrist who discovered the syndrome in the early 1950s.

Who are night eaters?

Estimates vary on how many people have this problem, but research suggests that it affects 6 to 8 percent of people treated in obesity clinics and about 1.5 percent of the general population, Stunkard says.

People of normal weight sometimes are affected, too, and it may be a pathway to the development of obesity, he says.

Penn researchers have studied more than 100 patients with the condition and also have gathered data from more than 2,000 others who've visited their Web site, www.uphs.upenn.edu/weight.

Night eaters are different from those who get up occasionally to snack or who consume a lot of food several times a week before bed.

Stunkard says night eaters often eat sparingly early in the day. "The disorder represents a shift of the biological rhythm of eating to later in the day," he says.

People with the syndrome may, for example, eat 700 to 800 of their 2,200 daily calories at night. They may eat peanut butter right out of a jar or chocolate cake or leftovers from dinner, Allison says.

Syndrome's impact

The emotional and physical impact is circular. "The eating helps soothe people and makes them feel better for a short time, but it also increases their weight, which makes them feel worse," she says.

Some are frustrated. "They feel like even though they are eating well during the day, they can't lose weight because they feel so compelled to eat during the night."

Allison worked with one woman who got up and ate more often at night after her third child was born with a serious brain abnormality. The increasing weight left her feeling depressed and hopeless.

Another patient woke nearly every hour on the hour and tried to do other activities but usually ended up giving in and eating. "Then I sleep like a baby," he reported.

Porreca didn't have a history of depression. He believes he had a sleeping disorder that became an eating disorder. "Between the two of them, it took hold and I couldn't control it," he says. When Penn doctors studied his eating patterns, they found he ate 34 percent of his calories between midnight and 4 a.m.

Common symptoms

Key behaviors observed in people with night eating syndrome:

• Overeating in the evening. They may feel hungry and eat to relax before bedtime.

• Difficulty falling asleep. They may toss and turn for half an hour or longer. They may need to eat something just before going to bed.

• Waking at night and eating at least three times a week. After falling asleep, they often wake up at least once and need to eat before being able to fall asleep again.

• Not feeling hungry in the morning. They don't have any appetite and will often go without food until lunchtime or later in the afternoon. They may wake up "feeling kind of gross, nauseated, like they're really full," Allison says.

For some people, the syndrome becomes part of their daily lives for years, she says. "We see people who are 60 and have had it since they were 30," she says.

Experts are researching treatments, including recommending basic behavioral changes in eating and exercise habits.

David Neubauer, an associate director of the Sleep Disorders Center at Johns Hopkins Medical School in Baltimore, says doctors at sleep clinics treat a range of sleep-related eating issues.

In the 1980s, researchers wrote about a problem called nocturnal sleep-related eating disorder. People suffering with this go to sleep, then get up and may not be fully aware that they are eating. Some know what they've done only after being observed or by noticing missing food, crumbs and empty wrappers, he says.

They are different from people who actually wake up and get a snack, but they may share some of the characteristics of people with the night eating syndrome, he says.