Is it bad to eat late at night?

NEW YORK – Many people reach for comfort foods such as ice cream and leftover takeout after a long day. But if you make late-night snacking a regular habit, it could have unintended consequences on your health, experts say.

According to a recent study of the eating habits of more than 34,000 adults in the United States, nearly 60 per cent said it was normal for them to eat after 9pm.

Human bodies have evolved to process nutrients during the day and to conserve and store energy at night, said Associate Professor Marie-Pierre St-Onge, a nutrition and sleep scientist at Columbia University. And disrupting that natural rhythm could cause problems, she added.

Several studies have found, for instance, that eating dinner within three hours of bedtime may worsen heartburn or acid reflux symptoms.

And limited research has suggested that eating one to three hours before bedtime is associated with more disrupted sleep.

The most intriguing research on late-night eating, however, has focused on its relationship with body weight and metabolic health, said neuroscientist Frank Scheer at Brigham and Women’s Hospital in Boston.

In one 2019 study of nearly 900 middle-aged and older US adults, for instance, Professor Scheer and his colleagues found that those who consumed roughly 100 calories or more within two hours of bedtime were about 80 per cent more likely to be overweight or to have obesity than those who did not eat during that window.

Researchers have found similar results in adults in Sweden and Japan.

And in a 2023 study of more than 850 adults in Britain, those who regularly snacked after 9pm had higher levels of HbA1c, a marker for diabetes risk, and greater spikes in blood sugars and fats after daytime meals than those who did not typically consume late-night snacks.

Such studies cannot prove that late-night eating directly causes weight gain or other health problems because other factors – such as one’s genetics, exercise and sleep – are also involved, he said. But recent research that controls for these factors has started to reveal direct effects of meal timing on health.

Why late eating might be harder on your body

In a 2022 trial, Prof Scheer and his colleagues asked 16 overweight or obese adults to live in a laboratory where their meals, exercise and sleep were carefully regimented.

All of the subjects followed two different eating schedules, each for six days. One schedule allowed for breakfast soon after waking, lunch at midday and dinner in the early evening; and the other shifted meals four hours later, with supper at around 9pm.

The participants consumed the same amounts of nutrients and calories on both routines. Yet, on the later meal schedule, they felt hungrier than they did on the earlier one. At the same time, their levels of the hormone leptin (which signals fullness) were lower throughout the day, and their levels of ghrelin (which signals hunger) were higher.

They also burned fewer calories. And several other small studies have found that people burn less fat on a late eating schedule.

Together, these findings suggest that late-night eating could cause weight gain, Prof Scheer said, though longer-term studies are needed.

Research has also found that carbohydrates consumed in the evening result in greater blood sugar spikes than those consumed earlier in the day, said Dr Erin Hanlon, a behavioral neuroscientist at the University of Chicago.

That is in part because melatonin, a sleep-promoting hormone that increases in the evening, dampens the secretion of insulin, which regulates blood sugar levels, she added.

Elevated blood sugars could eventually damage blood vessels and increase the risk of developing high blood pressure and Type 2 diabetes, Prof St-Onge said.

How to time your night-time eating

Research suggests that, if possible, it is best to avoid eating for three to four hours before your usual bedtime, Prof St-Onge said.

That timing is likely better for your long-term health, and may also reduce symptoms of acid reflux, which can interfere with sleep, Dr Hanlon added.

If you are a shift worker, eating late at night may be unavoidable. But if you can, Prof Scheer said, try to eat your largest meals between 7am and 7pm.

Timing your eating and sleeping can be a little bit of a juggling act, Prof St-Onge said. You do not want to eat a large meal too close to bedtime, but you do not want to go to bed hungry either.

Prof Scheer also cautioned that some people, such as those who struggle with low blood sugar or with getting enough nutrition, may need to eat at night.

If you do eat later in the evening, Prof St-Onge suggested opting for smaller, more nutritious meals or snacks that are not very high in fat or added sugars, such as plain yogurt with fruit, vegetables with hummus or almond butter on wholegrain toast. NYTIMES