Don't eat before you go to sleep—good advice or medical myth?

Last night, I had a big meal and then went to bed.  I felt full and thought about the medical myth that patients often ask me about—does eating late at night lead to weight gain?

I love busting medical myths. There are so many out there—and the Internet allows people to send them around so easily! In this article, my colleague Dr. Rob Shmerling explains the truth and myths behind the idea that you shouldn't eat before you go to sleep.

From Dr. Shmerling: Perhaps you've heard this advice before: Don't eat before going to bed. People most often give this advice to people trying to lose weight. The logic behind this advice sounds reasonable: If you eat and then go to sleep, your body will convert the food you ate into fat rather than using it right away as fuel. Ultimately, you'll gain weight.

But is this true? I have been unable to find any study that specifically asked and answered this question: When total calories are kept constant, does eating at night (whether just before bed or in the middle of the night) lead to weight gain?

In fact, I could find no compelling evidence that eating late at night or just before bed matters one way or the other. It is likely that total intake over a 24-hour period balanced against calories burned through one's daily activities matters much more than what time a snack or meal is consumed.

There are reasons other than concerns about weight to be careful when you eat. For people prone to heartburn (also called gastroesophageal reflux disease, or GERD), eating just before bed may cause trouble. When you lie down to sleep, the connection between the esophagus and stomach becomes horizontal instead of vertical. People with GERD often have more symptoms if they lie down after eating, whether it's bedtime or not. That's why people with GERD are routinely advised to raise the head of the bed (to maintain some element of gravity to keep acid in the stomach where it belongs) and not to eat shortly before going to bed.

I also have read reports of poor-quality sleep and nightmares as a consequence of eating before bed, but these are not well supported by evidence either. Perhaps the best advice in this regard is to rely on your experience. If eating at night seems to make it harder to sleep or has been associated with bad dreams, it's probably a good idea to avoid that late night snack. And if spicy or fatty foods seem particularly troublesome, avoid those.

Caffeine and alcohol deserve special mention. People who are sensitive to the stimulant effects of caffeine should avoid intake one to three hours before bed (or even longer if experiencing insomnia), While alcohol is a sedative that may promote sleep, alcohol-induced sleep commonly leads to awakening just a few hours later and difficulty getting back to sleep.

There is one type of nighttime eating that some experts consider an actual disease, night eating syndrome (NES). Its definition is still evolving, but it generally describes significant food intake that interrupts sleep.

One definition requires that a significant portion of the daily calorie intake occur after dinner, and that sleep is disrupted. An inability to return to sleep without eating is another feature of this condition.

There is no clear consensus regarding how common it is, its cause and how (or if) it should be treated. Preliminary studies suggest that antidepressants in the category of fluoxetine (Prozac) may help, but rigorous scientific trials have not yet been published.

It is possible that, for some people, eating at night is associated with weight gain. Perhaps they find it easier to be careful about portion size and food choices during the day but simply "lose it" at day's end. For some, the structure of three meals a day may make it easier to avoid excessive calorie intake.

But it's probably a myth that eating before bed has a unique ability to promote weight gain compared with eating at other times of the day. Although scientific studies someday may prove that calories ingested before bed are handled differently than calories ingested at other times, evidence for this commonly held belief is lacking. For now, it's safe to assume that one's weight reflects the balance between calories burned and calories consumed over time, regardless of when you choose to eat.

Do you limit how much you eat late at night? If so, do you do it to try to prevent gaining weight, or because eating at night disturbs your sleep?

Julie K. Silver, M.D., is an assistant professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School. She is also the Chief Editor of Books for Harvard Health Publications.

Sleep
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