Buzz
Research has raised concerns that eating late at night could contribute to weight gain. But how late is actually too late to have dinner? And more importantly, is there any real evidence that eating at night will cause weight gain?
Why Is Everyone Talking About Eating Late at Night?
If you’ve noticed this question appearing more frequently, it’s likely due to a recent study that looked at what happens when people eat their meals earlier in the day (breakfast, lunch, and dinner) versus later (lunch, dinner, and another late meal). The researchers found that those eating later were hungrier, burned fewer calories, and had fat cells showing genetic activity linked to fat gain.
It’s crucial to understand that this study did not examine whether participants actually gained or lost weight. Yes, you read that correctly: Despite the widespread headlines claiming that eating late is “harmful,” “impedes weight loss,” “increases obesity risk,” or is “something you should totally avoid,” the study did not track the participants' weight. The authors even state:
The goal of this study was to assess the immediate [short-term] impact of late-night eating on energy balance, not to investigate whether sticking to such a schedule long-term would lead to weight gain or if the body would eventually adjust allostatically.
In other words, it’s quite possible that your body would adjust to the new eating pattern if that became your lifestyle. (The participants followed the designated eating schedule for only six days at a time.)
What does additional research say about late-night meals?
Other studies suggest that eating late may make it easier to gain weight, but it’s not as simple as merely shifting meal times and expecting changes in body size.
For example, studies on mice have shown that when they are made to eat during the day (when they would normally be sleeping), they gain weight faster than mice that eat at night. However, these results don't directly apply to humans for several reasons. Firstly, the mice are typically young and still growing, which may not reflect what happens in adulthood. Secondly, they are mice, not humans. (A small but important detail.)
Healthline has an excellent summary here of the human research to date. A lot of it contradicts the idea that late-night meals cause weight gain. For example, there are many studies that show meal timing doesn't make much difference when calories are controlled. This makes perfect sense when you think about it.
What you consume is more significant than when you eat it
The idea that late-night meals contribute to weight gain has been around for quite some time, and it’s evolved into several myths that don’t hold up against scientific evidence. For instance, it's a myth that your body “doesn’t burn” calories from food eaten late at night. Your body burns calories constantly, even while you’re asleep. In fact, most of your calorie burn occurs when you’re resting.
Research on late-night eating has shown that people who eat later tend to consume more calories than those who eat earlier, and they’re also more likely to choose processed, high-calorie foods. The recent study mentioned above found that those in the late-meal group felt hungrier, which aligns with these findings.
Once again, there may be other factors at play here. If you're eating late, it could be because you're up studying late or working the night shift. In these situations, you might not have the time, energy, or resources to prepare a nutritious meal. Instead, you might grab chips and soda or order from a late-night pizza joint. It's also possible that working overnight is impacting your circadian rhythm, making late meals an effect rather than the cause. Lack of sleep has been shown to contribute to weight gain.
Looking back at the recent study, those who ate late meals experienced about a 5% reduction in the number of calories burned by their bodies. While this is an average and not universally true—some people burned slightly more calories on the late-night diet. A 5% decrease equals roughly 115 calories for someone consuming 2,300 calories daily (the average for American adults). This is about the same as one banana or a one-ounce slice of cheese. Even if this effect persisted beyond the six-day study, you could counteract it by reducing your intake by one ounce of cheese daily.
For similar reasons, Winchester Hospital advises eating earlier if possible. However, they also suggest: 'If you miss a healthy dinner at 6:00 p.m., there’s no reason not to have it at 9:00!'
Late meals may affect your sleep quality.
Personally, I avoid eating too late, but not necessarily due to concerns about weight gain. I simply find that my sleep quality tends to suffer when I eat close to bedtime. (I also tend to eat healthier overall when I eat earlier. This is likely because I’ve had time to plan my meals, rather than waiting until I’m exhausted and scrambling to prepare something quick before bed.)
This is the usual advice you'll hear from sleep tracker brands like Whoop. However, science doesn't always support this. The study we referenced earlier revealed that participants in both groups had similar sleep quality. Other research, such as this one, even suggests that late dinners could actually improve sleep quality. In that particular study, people who ate later in the evening experienced more deep sleep during the early part of the night.
If you're worried about how late meals might impact your sleep, try eating earlier and monitor if it results in a better night's rest. For instance, keep track of how refreshed you feel the following morning and make adjustments based on your observations.
So, how late is too late?
Alright, what if you decide to experiment with earlier meal times? Even though it's unlikely to be a miracle cure for weight loss, it might still be worth giving it a try.
In the study we referenced at the beginning of this article, participants who ate a late meal did so two and a half hours before bedtime—so, for example, at 8:30 p.m. if they went to sleep at 11. Those who had earlier meals dined about four hours earlier—around 4:30 p.m. in this case.
There is a type of intermittent fasting that some believe may be more effective for syncing our body’s circadian rhythm. While the research on this is limited, it's worth mentioning that those who follow this approach typically eat between 8 a.m. and 6 p.m.
The guidance on avoiding late meals typically falls within these time frames. For example, Oura, a sleep tracker brand, suggests having your last substantial meal at least three hours before bed—ideally around 8 p.m. if you're going to sleep at 11. Additionally, if you're trying to prevent heartburn, medical experts generally recommend finishing your final meal at least three hours before sleep, with some advising a four-hour gap.
Taking all of these considerations into account—and using the example of an 11 p.m. bedtime—you might want to have dinner no later than 7 p.m. to ensure you’re finished by 8 p.m. and your stomach is empty or nearly empty by bedtime. If you must eat later, be especially mindful of your food choices, and aim to eat the same meal you would typically have for dinner—even if that means preparing a healthy meal earlier in the day to avoid the temptation of ordering takeout.
