Chips, dips, cookies, chocolates, eggnog: These are among the temptations posed by the highly palatable, high-calorie snacks commonly served at winter evening social events that intensify the struggle people with night eating syndrome (NES) face year round.

People with NES overeat in the evening and even awaken from sleep to eat one to two times a night on average, according to Kelly Allison, Ph.D. They consume one-quarter or more of their daily food intake after their evening meal, said Allison, a research assistant professor of psychology in psychiatry at the University of Pennsylvania School of Medicine and director of a NES-focused cognitive-behavioral therapy (CBT) study.

People with NES typically lack appetite in the morning. Some curb their daytime food intake, knowing they will graze after dark.

NES was first described in 1955 by Albert Stunkard, M.D., a professor of psychiatry, director emeritus of the University of Pennsylvania's weight and eating disorders program, and still an active investigator in the field.

While holiday-related stress boosts NES in some people, whether reduced winter daylight exposure also contributes to the disorder is still being explored. Allison, Stunkard, and colleagues are tracking people with NES and control subjects in Philadelphia and Stockholm, Sweden, in winter and summer to see if eating behavior varies by season.

Occurring in about 1.5 percent of the general population, NES is more common than anorexia nervosa, which affects less than 1 percent of the population, mainly young women, Stunkard said. People with NES rarely binge and purge.

About 7.6 percent of obesity clinic patients report symptoms of NES, as do 12 percent of those visiting outpatient psychiatric clinics for any disorder. Among people awaiting bariatric surgery, 10 percent to 27 percent have NES, two studies have suggested. DSM-IV-TR classifies NES as an eating disorder not otherwise specified.

Not all people with NES are obese. Some maintain normal weight via daytime food restriction or intensive exercise. These individuals typically are younger by about a decade than obese people with NES, suggesting NES may serve as a pathway to obesity, Stunkard noted.

Many people with NES keep a small refrigerator next to the bed, favoring peanut butter, popsicles, candy bars, nuts, and sometimes fruit as handy middle-of-the-night snacks. They rely on food as an aid to returning to sleep, probably a conditioned response, Allison reported.

People with NES remember what they eat in the night, unlike people with sleep-related eating disorder (SRED), a rare parasomnia. Those with SRED often have only partial recall of having consumed frequently unpalatable items, such as buttered cigarettes, raw bacon, or cat food.

Allison, Stunkard, and colleagues assessed 25-hour profiles of circulating glucose and seven hormones in relation to food intake, sleep, and stress in 15 women with NES and 14 matched controls, reporting results in the November 2005 Journal of Clinical Endocrinology and Metabolism.

Participants spent three nights in a general clinical research center at Penn. They received three meals a day and had ad libitum access to snacks, including foods brought from home, placed on a bedside table at night.

Both groups had a similar total daily caloric intake, averaging about 2,900 kcal. NES subjects ate far more at night, consuming four times more fat and twice the amount of carbohydrates and protein between 8 p.m. and 8 a.m. than control subjects. All NES subjects awakened to eat at least two of their three nights in the hospital, compared with only one control subject.

"We found no evidence of an endocrine etiology for night eating in this very careful study," Stunkard said. This work, he added, corrects findings from an earlier, smaller study suggesting NES might involve a disturbance of appetite-regulating hormones.

"We think NES represents a dysregulation of circadian patterns of food intake, but without disruption of the circadian sleep pattern," he explained. "NES is primarily an eating disorder, and only secondarily a sleep disorder." While appetite normally shuts down in sleep, NES appears to be a rare clinical example of an uncoupling of eating and the sleep/wake cycle. Its cause has not been determined.

John O'Reardon, M.D., an assistant professor of psychiatry at Penn, working with Allison, Stunkard, and others, randomly assigned 17 outpatients with NES to receive sertraline and another 17 to receive placebo in an eight-week, double-blind, flexible-dose (50 mg to 200 mg a day) study. They found 12 subjects in the sertraline group, but only three in the placebo group, much improved or very much improved, according to the Clinical Global Impression of Severity Scale. Overweight and obese subjects in the sertraline group lost more weight by week 8 than those on placebo. The researchers' report is in press with the American Journal of Psychiatry.

In a novel long distance study, perhaps the first of its kind, according to Stunkard, the Penn team recruited 50 patients who described symptoms consistent with NES on a website questionnaire, and whose physicians agreed to provide treatment with sertraline for eight weeks at dosages suggested by the Penn investigators. Patients completed survey forms every two weeks. Success rates were comparable to those in the single-and double-blind trials. A report is in preparation.

Allsion, meanwhile, enrolled 16 adults with NES in a 10-session, 12-week trial of NES-focused CBT, the first study of CBT for the disorder.

Since many people with NES eat chaotically in the daytime, Allison encouraged them to keep food diaries, eat more systematically, and choose snacks smaller and lower in calories. She also advised them to get food out of the bedroom. "Once they do that," she said, "they have less reason to wake up, so they awaken less often."

Nine subjects completed the study, cutting their middle-of-the-night snacking from six to 0.3 times per week. Completers also lost a significant amount of weight by the study's end, she reported at Obesity Society meetings in Vancouver, British Columbia, in October 2005.

"While people with NES who stay on sertraline continue to do well," Allison notes, "learning CBT strategies may give them a better long term prognosis."

Resources for patients about night eating syndrome include Overcoming Night Eating Syndrome: A Step-By-Step Guide to Breaking the Cycle by Kelly Allison, Ph.D., Albert Strunkard, M.D., and Sara Their (New Harbinger Publications, 2004) and the University of Pennsylvania Web site at<www.med.upenn.edu/weight/nighteating.shtml>.▪