Is it really bad for your health to eat late at night?

Question: “I heard that eating late at night is harmful to your health. That is true?“

Many of us turn to comfort foods like ice cream and leftovers after a long day. But if you make late-night snacking a regular habit, it could have unintended consequences for your health, experts say.

According to a recent study of the eating habits of more than 34,000 U.S. adults, nearly 60% said it was normal for them to eat after 9 p.m.

Our bodies evolved to process nutrients during the day — and to conserve and store energy at night, said Marie-Pierre St-Onge, a nutrition and sleep scientist at Columbia University. And disrupting that natural rhythm can cause problems, he said.

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

Additionally, limited research has suggested that eating one to three hours before bed is associated with more disrupted sleep.

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

In a 2019 study of nearly 900 middle-aged and older adults in the U.S., for example, Scheer and his colleagues found that those who consumed about 100 calories or more within two hours of bedtime were about 80% more likely of being overweight or obese than those who did not eat during this period. Researchers found similar results in adults in Sweden and Japan.

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And in a 2023 study of more than 850 adults in Britain, those who snacked after 9 p.m. had higher levels of HbA1c, a marker of diabetes risk, and greater spikes in blood sugar and fat after daytime meals. compared to those who did not usually consume nighttime snacks.

These studies cannot prove that eating late at night directly causes weight gain or other health problems, because other factors, such as genetics, exercise and sleep, are also involved, he said. But recent research controlling for these factors has begun to reveal direct effects of meal timing on health.

Why Eating Late Can Be Harder on Your Body

In a 2022 experiment, 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 participants followed two different eating routines, each for six days: one allowed breakfast right after waking up, lunch at noon and dinner in the early evening; the other delayed meals by four hours, with dinner around 9pm.

Participants consumed the same amounts of nutrients and calories in both routines. However, in the later meal routine, they felt hungrier than in the previous routine. At the same time, their levels of the hormone leptin (which signals satiety) were lower throughout the day, while 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 routine.

These findings suggest that late-night eating may cause weight gain, Scheer said, although long-term studies are needed.

Research has also found that carbohydrates consumed at night result in greater blood sugar spikes than those consumed earlier in the day, said Erin Hanlon, a behavioral neuroscientist at the University of Chicago. This is partly due to the fact that melatonin, a hormone that promotes sleep and increases at night, decreases the secretion of insulin, which regulates blood sugar levels, he added.

Rising blood sugar levels can eventually damage blood vessels and increase the risk of developing high blood pressure and type 2 diabetes, St-Onge said.

How to schedule your nighttime eating

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

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

If you work shifts, eating late at night may be unavoidable. But if you can, Scheer said you should try to eat your biggest meals between about 7 a.m. and 7 p.m.

Scheduling your eating and sleeping can be “a little tricky,” St-Onge said. You don’t want to eat a big meal too close to bedtime, but you also don’t want to go to bed hungry.

Scheer also warned that some people, such as those who struggle with hypoglycemia or who can’t get enough nutrition, may need to eat at night.

If you eat later at night, St-Onge suggested opting for smaller, more nutritious meals or snacks that aren’t too high in fat or added sugars, such as plain yogurt with fruit, vegetables with hummus, or almond butter on whole-grain toast.