Waking up in the middle of the night is an annoying event that most of us experience. Usually we are able to fall asleep again quickly, perhaps after drinking some water and/or making a trip to the bathroom. But for some, waking up is a signal to go into the kitchen and eat: a bowl of cereal, a peanut butter sandwich, or a dish of ice cream. And unhappily, going back to bed after the night time snack does not ensure that the remainder of the night will be restful. Waking may occur once again, or even several times during the rest of the night, and is always accompanied by eating. The next morning, the night time eater has no appetite for breakfast and may not eat for hours.
When the pattern of awakening and eating occurs regularly, it is defined as a type of eating disorder called Night Eating Syndrome (“NES”) described first by Albert Stunkard in l955. Dr. Stunkard was a professor of psychiatry at the University of Pennsylvania when he first put forth the criteria for diagnosing this poorly understood behavior. Simply eating leftover pie or pizza at midnight is not sufficient to meet the diagnosis, because people with NES consume about 25% of their total daily calories after the evening meal. The food can be consumed in the evening before sleep and/or during nocturnal awakenings. Those with NES suffer from insomnia at least four or five times a week and believe that they will not be able to go back to sleep unless they eat. Finally, if they have mood disturbances like depression and anxiety, their moods will worsen as the evening progresses.
Interestingly, as Stunkard points out in a paper he wrote on the subject almost fifty years later, people who engage in frequent night time eating are not necessarily obese, although it is a risk factor for obesity. Because they are unlikely to eat during the early part of the day, (skipping breakfast and delaying lunch) their total daily intake may be appropriate. On the other hand, many who are seeking help for their obesity often fail to report nighttime eating episodes. Plus, they are rarely asked about it, so it is not known to what extent this type of eating contributes to weight gain.
The inability to sleep through the night, or to do so with only infrequent awakenings of short duration, is certainly associated with NES, but is it the cause? Many people have insomnia, but they do not eat their way through every period of nighttime wakefulness. If the food eaten helps put the eater back to sleep, this would explain their seeking food once they wake up. But it is hard to find studies that test whether the foods chosen in order to put the insomniac to sleep actually work. Moreover, in a study that examined sleep cycles of NES subjects and controls, no difference was found in the duration of sleep, although the former did awaken earlier in the night and more often.
Perhaps the syndrome is not caused by disordered sleep, but by something else. Current research suggests someone with NES is not eating to go back to sleep, but rather waking up because of hunger. The “hunger” hormone ghrelin, which normally is secreted during the day when we normally feel hungry, seems to peak late in the evening and into the night in NES sufferers. Thus they may be awakening because of ghrelin-potentiated hunger.
A solution has been to reset the pattern of ghrelin secretion back to normal by exposing the patient to light very early in the morning. Anyone who has traveled east across enough time zones to feel out of sync and out of sorts during the first couple of days, knows the feeling of being forced to sleep and eat on another time zone’s timetable. It is hard to be hungry for breakfast when it is only 3 am back home, and it is hard to find food when you wake up hungry at 2 am because it is now 7 pm back home. If you stay in the new time zone long enough, your eating and sleeping hormones adjust. This is what researchers hope to accomplish for the night eaters using bright lights to make ghrelin levels high during daylight rather than at night.
Melatonin is also being tried because some studies have found that this sleep hormone is not as high as it should be in the late evening, and perhaps this is why it is so easy for the night eaters to wake up. There is a time-released melatonin preparation containing the low recommended dose of melatonin (0.3 mg); whether it might prevent frequent awakenings has not yet been tested. Anxiety and depression are also linked with NES, but it is unclear if they are the cause or consequence of disrupted sleep.
It is not unusual to wake up at 3 am and be assaulted with the worries that were successfully repressed 12 hours earlier. If one were prone to depression and anxiety, would these mood disorders cause sleep disturbances leading to frequent awakenings or, if awake, prevent the individual from falling back asleep unless something is eaten? Stunkard recommended antidepressants that increase serotonin activity to decrease anxiety and depression and calm the individual back into sleep. But a remedy that would help the sleep, as well as hunger and mood disturbances, is more simple and natural: a cup of low-fat, mildly sweet breakfast cereal eaten upon nighttime awakening. The carbohydrate will increase serotonin thus inducing relaxation, satiety and a more tranquil mood.
If the cereal is in a cup by the bed, it can be eaten without leaving it (as long as there are no crumbs.)
“The night-eating syndrome; a pattern of food intake among certain obese patients,” Stunkard, A.J.; Grace, W.; Wolff, H.,The American Journal of Medicine. 1955: 19: 78–86
“Two forms of disordered eating in obesity: binge eating and night eating,” Stunkard, A. and Allison, K.. Int J Obes Relat Metab Disord 2003, 27: 1-12
“Circadian eating and sleeping patterns in the night eating syndrome,” O”Reardon, J., Ringel, B., Dinges, D., et al, Obes Res. 2004; 12:1789-96