Night eating syndrome (NES) is an eating disorder characterized by an abnormal circadian pattern of food consumption; specifically, the patient eats 25% or more of his or her daily calories after the evening meal and/or awakens during the night two or more times per week and eats in order to fall asleep again. First described in 1955 by Albert Stunkard (1922–2014), an American psychiatrist and specialist in eating disorders, NES was not included in the Diagnostic and Statistical Manual of Mental Disorders until the fifth edition (DSM-5), published in 2013. Night eating syndrome is presently classified under the heading of Other Specified Feeding or Eating Disorder (OSFED), which replaces the earlier category of Eating Disorder Not Otherwise Specified (EDNOS). OSFED covers disordered eating or feeding patterns that cause significant emotional distress and impairment in the patient's occupational, educational, or social functioning but do not meet the full criteria for anorexia nervosa, bulimia nervosa, or binge eating disorder (BED).
NES is estimated to affect between 1%–2% of the general adult population in North America, and as many as 10% of obese adults. It is most common in young and middle-aged adults; the syndrome is rarely reported in children. Men are slightly more likely than women to be diagnosed with NES. As far as is known as of 2018, people of any race or ethnic group may develop NES.
Night eating syndrome was first described in 1955 as an eating pattern contributing to obesity characterized by “nocturnal hyperphagia, insomnia, and morning anorexia.” In other words, the patient has an increased appetite at night combined with difficulty falling or remaining asleep, and lowered appetite in the morning. NES received little attention after 1955 until the 1990s, when the sharp increase in the rates of obesity and eating disorders in the developed countries led researchers to look more closely at the relationship between weight gain and disordered eating patterns.
Risk factors for night eating syndrome include:
The causes of NES are not known as of 2018, although some researchers think that genetic factors may play a part. One gene on human chromosome 17 known as PER1 codes for a protein that regulates circadian rhythms in a part of the brain called the suprachiasmic nucleus (SCN) and may have a protective effect against cancer. Researchers do not know for certain as of 2018 whether variations (polymorphisms) in this gene contribute to the risk of developing NES or other disorders of the sleep/wake cycle, but research is ongoing.
Other proposed causes of NES include learned behavior patterns in regard to food, employment patterns that involve late-night or all-night work combined with opportunities to eat, general difficulty in managing stress, and/or beliefs about the relationship between eating and sleep.
The symptoms of NES are distinguished from those of other eating disorders as follows:
Patients who are suspected of night eating syndrome are often already under medical care for comorbid disorders (usually diabetes, depression, obesity, or PTSD) but may be given a physical examination to check for changes in the symptoms of these other disorders or to rule out substance abuse or side effects from medications that the patient is already taking.
The most common test for NES is a questionnaire devised in 2004 by researchers at the University of Pennsylvania Center for Weight and Eating Disorders (CWED) called the Night Eating Questionnaire (NEQ). The questionnaire has 14 items inquiring about the patient's eating and sleeping habits, mood at different times of day, control over eating, time of first meal, and other similar questions. Some of the test items are added together to yield a total score, whereas other questions are used to rule out SRED. The authors of the NEQ suggest discussing the results with the patient before making a final diagnosis of NES because many people overestimate the amount of food they eat at night.
Some doctors will also recommend polysomnography, which is a test performed in a laboratory while the patient is sleeping. Electrodes attached to the patient's body allow the technologist to record and measure such functions as brain waves, eye movements, heart and breathing rates, skeletal muscle activity, blood oxygen levels, and other functions.
Medications were the first treatments tried for NES beginning around 2003. The first drugs that were used were selective serotonin reuptake inhibitors (SSRIs), specifically paroxetine (Paxil) and fluvoxamine (Luvox). Later, sertraline (Zoloft), another SSRI, was used in clinical trials to treat NES, with good results; 71% of patients reported fewer nighttime awakenings, less food consumed during nighttime awakenings, and lower calorie intake after the evening meal.
As of 2018, escitalopram (Cipralex, Lexapro), still another SSRI, has been used in three clinical trials (all in the United States) for the treatment of NES. Preliminary findings indicate that escitalopram is as effective as sertraline in treating NES.
Hypnotics such as zolpidem (Ambien) or over the-counter sleep medications are not recommended for patients with NES. Those who were given hypnotics reported having episodes of SRED and/or eating more food when they awoke at night than they usually consumed.
Nonpharmacological approaches to treating NES include progressive muscle relaxation (PMR), bright light therapy, and cognitive behavioral therapy (CBT). PMR appears to be effective in helping patients fall asleep as well as reducing stress and fatigue. Bright light or phototherapy began in 1984 as a treatment for seasonal affective disorder (SAD), a type of mood disorder in which people with normal mood most of the year experience depression during the winter as a result of decreased sunlight. Because NES is associated with disturbances in patients' circadian rhythms, phototherapy has been tried to help NES patients reset their biological clocks. Several case studies indicate that bright light therapy is effective in some NES patients.
CBT for patients with NES focuses on changing the patient's beliefs related to eating as an aid to sleep after waking up at night. The strategy involves encouraging patients to eat more food earlier in the day and restructuring thought patterns that identify food as an effective way to return to sleep.
Melatonin, a hormone that regulates the human sleep/wake cycle, is available in over-the counter formulations in both the United States and Canada. Frequently recommended to treat insomnia in the elderly, shift workers, and travelers with jet lag, melatonin appears to be helpful to some patients with NES, although others find it ineffective. Melatonin is currently being used in one clinical trial of male veterans diagnosed with NES at a Veterans Administration hospital in Connecticut.
The chief dietetic or nutritional concern for patients with NES is weight gain and its associated risks of type 2 diabetes, depression, and cardiovascular disorders. Although not all patients diagnosed with NES are obese, many are, and the disorder severely complicates efforts to lose weight. What is unclear as of 2018, however, is the cause-and-effect relationship between NES and obesity. Researchers are not yet certain whether obesity is the cause of NES or its result.
Although more clinical studies of NES need to be done, most patients diagnosed with the disorder report at least short-term benefits from antidepressant medications and/or PMR and bright light therapy. CBT appears to be less successful as a treatment modality. NES, however, has not been studied closely over a long enough time for researchers to have a clear picture of its long-term prognosis.
People can lower their risk of developing NES by eating a healthful diet, getting regular physical exercise, keeping to a regular pattern of sleeping and waking, and learning effective stress management techniques. Any genetic factors that may be linked to the disorder, however, cannot be changed with current treatment techniques.
See also Eating disorders ; Nutrition and mental health ; Obesity .
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American Diabetes Association (ADA), 2451 Crystal Dr., Ste. 900, Arlington, VA, 22202, (800) 342-2383, http://diabetes.org .
American Psychiatric Association (APA), 800 Maine Ave. SW, Ste. 900, Washington, DC, 20024, (202) 559-3900, firstname.lastname@example.org, https://www.psychiatry.org .
National Eating Disorders Association (NEDA), 200 W. 41st St., Ste. 1203, New York, NY, 10036, (212) 575-6200, (800) 931-2237, Fax: (212) 575-1650, info@NationalEatingDisorders.org, https://www.nationaleatingdisorders.org .
Perelman School of Medicine, University of Pennsylvania, Center for Weight and Eating Disorders (CWED), 3535 Market St., Ste. 3108, Philadelphia, PA, 19104, (215) 898-7314, Fax: (215) 898-2878, http://www.med.upenn.edu/weight .
Rebecca J. Frey, PhD