Night Eating Syndrome
Defined As New Eating Disorder

NEW YORK - People who don't eat anything until around dinner time, but who can't stop eating until almost morning, may have a new eating disorder that is quite unlike either anorexia or bulimia nervosa, investigators suggest.
A report on "night-eating syndrome" is published in Wednesday's issue of The Journal of the American Medical Association.
Dr. Grethe Stea Birketvedt from the University of Pennsylvania School of Medicine in Philadelphia, and colleagues from there and from the University Hospital of Tromso, Norway, compared behavior in 10 obese subjects whose eating behavior was characterized by lack of appetite in the morning, followed by a large consumption of calories during the evening and at night, with that of 10, similarly obese control subjects who were not night eaters.
Although the amount of food consumed by the two groups was only "modestly" different, "the pattern of daytime and nighttime food intake of the two groups differed dramatically," the researchers point out. For example, night eaters recorded 9.3 eating episodes during the 24-hour study period compared with 4.2 eating episodes recorded by controls.
Between 8 p.m. and 6 a.m., "night eaters consumed 56% of their (daily) energy intake compared with 15% consumed by the control subjects," investigators add. On average, night eaters also woke up far more often during the night than did controls, and on approximately half of these awakenings, night eaters would consume roughly 250 calories in the form of a snack " 70% of which was in the form of carbohydrates. In comparison, none of the controls ate during their nighttime awakenings, the team points out.
In a related study, Norwegian investigators compared hormonal patterns between 12 night eaters and 11 overweight subjects who did not eat at night, again over a 24-hour period. Seven out of the 12 night eaters in the Norwegian study were not obese.
"As in the behavioral study,... nighttime awakenings were far more common among the night eaters... than among the controls," the Norwegian investigators observe.
Compared with controls, the group also found that blood levels of the hormones melatonin and leptin did not go up to the same extent as they did in controls. Melatonin is thought to help people fall and stay asleep, while leptin is believed to suppress appetite.
Between 8 a.m. and 2 a.m., levels of cortisol, another hormone, were also higher in night eaters than in controls.
"Contrary to the usual pattern found in depression, the mood of the night eaters (also) fell during the evening," the group adds.
Birketvedt told Reuters Health that night eaters are quite distinct from people with the eating disorder bulimia nervosa, who may eat huge amounts at one sitting but who do not snack all the time. In contrast, night eaters, "eat little until dinner time, after which they can't stop eating almost until the morning," she said.
When night eaters wake up in the middle of the night, "they also wake up wanting to eat, not particularly because they are hungry but because they have this urge to eat," Birketvedt added.
Birketvedt estimated that up to 1.5% of the adult population in many countries including the United States have this pattern of disordered night eating. Because so many people are affected by the syndrome, "these findings are important," she felt.
In an accompanying editorial, Dr. Joel Yager from the University of New Mexico School of Medicine in Albuquerque, suggested that more study is required "before the exact importance of these findings is known."
He also expressed reservations about whether supplemental melatonin or leptin suggested by investigators as potential treatments for night eaters "will prove clinically useful."