All-night diner

If you’re spending more time each night in the kitchen than in the bedroom, you may have a newly identified eating disorder. Called night-eating syndrome (NES), the condition is characterised by a lack of appetite for breakfast; the consumption of more than 50 percent of daily calories after the evening meal, and waking up, at least, once a night to consume high-carbohydrate snacks. To receive a diagnosis of NES, symptoms must have continued for a minimum of three months.

If you’ve never heard of NES, it’s not surprising. Awareness is only now increasing, as new research has appeared, led largely by Grethe Stoa Birketvedt, M.D. Ph.D., a research professor at Mount Sinai School of Medicine in New York City. Dr Birketvedt’s most recent major study on NES, co-authored with the American scientist who named NES back in 1955, Albert J. Stunkard, M.D. of the University of Pennsylvania, appeared recently in the Journal of the American Medical Association (JAMA). Their research found some intriguing evidence that three hormones play a significant role in causing this eating disorder. Firstly, Dr. Birketvedt and her colleagues at the University of Tromso in Norway found that levels of melatonin – the hormone that helps us fall asleep and stay asleep at night – were significantly reduced in NES sufferers. Similarly, leptin – the hormone that suppresses appetite – didn’t rise to normal levels in night-eaters, suggesting that their hunger pangs may be extreme enough to disturb sleep. Finally, cortisol – what’s often called the ‘stress hormone’, that kicks in when we’re feeling tense – was elevated at night in the group with NES, perhaps further enticing them to wake up and head to the kitchen.

Hormonal imbalances are probably not the whole story, however. Birketvedt believes that NES has a hereditary component which is not yet understood. ‘I’ve worked with 24 families in Norway who say they have NES in their family. We believe that it’s genetic, but I don’t think the primary cause is genetic in all night-eaters.’ There may well be psychological and emotional components, too, though Birketvedt doesn’t think these are mostly to blame. ‘NES can start at any time in someone’s life,’ she says. ‘It doesn’t need to be a time of psychological difficulty, stress, or even a depressed time.’

Nor is NES the sole province of the overweight or obese, though the incidence of the syndrome is higher in these groups. Overall, Birketvedt and Stunkard estimate that NES affects approximately 1.5 percent of the general population worldwide, and other research has found that up to 27 percent of obese people are night-eaters. ‘But worldwide, 50 percent of night-eaters are thin and 50 percent are overweight,’ says Birketvedt.

With much still unknown about NES, treatment is tricky. So far, little research has been conducted to address whether supplements of melatonin (available only in the U.S.) and/or leptin would work to help night-eaters get their hormones back on track. Somewhat more work has been done to look at the benefits of selective serotonin reuptake inhibitors (SSRIs), a type of antidepressant. The JAMA study theorised that because night-eaters overwhelmingly seek out high-carbohydrate snacks, which calm and satisfy the body, they may in effect be trying to elevate serotonin levels which help to encourage sleep. If that holds true, then SSRIs might work even more efficiently to achieve that benefit. Along the same lines, Birketvedt has prescribed NES sufferers a special diet, including foods high in tryptophan (such as turkey and peanut butter), an amino acid which also helps to induce sleep. It may also help some night-eaters to find ways to reduce stress and to plan social events in their evenings, thereby circumventing the opportunity to eat, at least in the early part of the night.

Do You Have Night-eating Syndrome?

• You eat 50 percent or more of your daily food intake after dinner
• You have no appetite for breakfast
• You have trouble falling and/or staying asleep
• When you wake up during the night you often eat
• The foods you eat at night are mostly carbohydrates

If you have any combination of these signs, consult your doctor.