Are you a nighttime nosher? Maybe you should see a doctor

Buttered popcorn and candy at the cinema late in the evening. Takeaway fish and chips on the way home from a party at night. Almost everyone indulges in some nighttime noshing now and then.

An estimated 1.5 million people in Germany alone even wake up during the night to cop some munchies, according to Dr Martin Teufel, director of the Clinic for Psychosomatic Medicine and Psychotherapy at Essen University Hospital and former president of the German Society on Eating Disorders (DGESS).

There are many possible causes. It can also be a symptom of night eating syndrome (NES), an eating disorder accompanied by frequent sleep interruptions to eat.

When is nighttime eating considered to be a disorder?

A person diagnosed with NES eats excessively at late hours, including after having fallen asleep.

"At least 25% of their daily calorie intake regularly occurs at night," says Dr Anja Hilbert, professor of behavioural medicine at the University of Leipzig Medical Centre, adding there has so far been too little research to scientifically define what "regularly" means in this regard.

Kelly C. Allison, professor of psychology in psychiatry at the Perelman School of Medicine at the University of Pennsylvania and director of the Center for Weight and Eating Disorders, has proposed the following criterion: NES is present if nighttime eating occurs on at least two days a week for at least three months.

This doesn't suffice for a diagnosis, however, because it also applies to shift workers with little opportunity to eat during daylight hours. "What distinguishes night eating syndrome is an additional, psychological component," explains Hilbert.

Some people with NES become overweight or obese and can develop sleep problems that make it more difficult for them to function during the day. They may also feel guilty or ashamed on account of their behaviour.

How prevalent is NES?

About one in 100 people have it, according to current research. "The number of unrecognized cases is probably high," Hilbert says, since "neither specialists nor the persons affected know much about it."

It can be difficult to distinguish from binge eating disorder, for example.

The causes and risk factors for NES remain largely unclear. Researchers see a connection between NES, anxiety disorders and depression. "If you're depressed or anxious, 'emotional eating' is a natural strategy," says Hilbert.

Stress could be a further risk factor, and scientists surmise that genetics may play a role as well.

People who are overweight or obese are more likely to have NES.

How does NES differ from other eating disorders?

"In contrast to many other eating disorders, it's also common in men," notes Teufel.

Another important difference is that the circadian rhythm, or "internal clock," of people with NES is disrupted. "In the research literature are indications that not only sleep and wake times are irregular, but also hormones are out of kilter," Hilbert says.

Possibly affected are the hormones melatonin, which helps people to fall asleep, and leptin, which regulates satiety and keeps you from feeling hungry at night. Whether an imbalance of these hormones causes nighttime eating, or rather results from it, is still unknown though, points out Hilbert.

When should you seek help?

If you regularly eat late in the evening or at night but don't suffer psychologically, physically or socially from it, there's no reason to see a doctor, Teufel says. "But if you realize that you can't stop, don't sleep well or develop a negative body image, then you should do something about it."

Hilbert takes a similar view: "An important criterion for treatment is suffering or feeling impaired."

How is NES treated?

Treatment options include cognitive behavioural therapy aimed at adopting healthier habits, and light therapy, which helps to change your circadian rhythm. Which treatment method is best depends on the individual patient, Teufel says.

The first thing that someone concerned about their nighttime eating should do is see their GP. If weight gain is part of the problem, nutrition counselling is a good idea as well.

"And if you've got the feeling you could use more help," adds Teufel, "it may be advisable to see a psychotherapist specialized in eating disorders."