DOES EATING LATE MAKE YOU FAT?

The Binge Bulge

Eating after 8 p.m. may increase the risk of obesity, according to a  study at Northwestern University. A five-year study on weight changes in college students which Dr. Hoerr is working on also suggests that eating late disrupts sleep patterns. "Our data shows that those who got the most sleep were more likely to maintain a healthy weight," she says. Researchers still don't know all the reasons why poor sleep is correlated to weight gain.

Bad Snacks vs. Good Snacks

Specific foods, she says, interfere with sleep. Avoid anything high in tyramine, a naturally occurring chemical that helps regulate blood pressure and can keep you awake, at least an hour or two before bedtime, says Dr. Hoerr. This includes aged cheeses, processed meats and soy sauce. High-protein and fatty treats should also be avoided because they take longer to digest. The good news: Some foods, when eaten in small amounts (under 200 calories), may actually aid in quality sleep, and not add inches to the waistline. Unprocessed turkey and nonfat milk are both high in the amino acid tryptophan, which can be converted to serotonin and melatonin—neurotransmitters that help promote good shut-eye. Foods high in the minerals magnesium (almonds), potassium (bananas) and calcium (low-fat yogurt) encourage muscle relaxation, and are OK to eat before bedtime. "The glucose in honey is easily digestible and comforting, which explains why a warm cup of milk sweetened with honey might be an ideal bedtime snack," says Dr. Hoerr.

Teenagers: The Exception

When teens hit their growth spurt, they almost can't eat enough, says Dr. Hoerr. "This is when you see an 11-year-old boy consuming more than the active man of the house," she says. "He should have extra snacks, like those suggested. The snack should be finished more than an hour before he goes to sleep."

Eat Early, Not Late

How can you kick a late-night eating habit? Try breakfast. "If you don't eat too close to bedtime, by morning, your liver has fully processed the sugar and fat and protein and your appetite is stimulated," she says. Many of Dr. Hoerr's overweight patients report to not eating anything until 3 p.m. and then they'll cram in thousands of calories by midnight. Invariably, their sleep quality is disrupted, and they put on more weight

A version of this article appeared July 2, 2013, on page D3 in the U.S. edition of The Wall Street Journal, with the headline: BURNING QUESTION | Is bedtime snacking bad?.