Anyone who’s ever laid awake in bed with acid reflux or digestive issues knows how the timing of your last meal can impact your sleep. But science shows ill-timed meals do more than just keep you awake.
Late-night meals can lead to everything from weight gain to type 2 diabetes. And they can mess with your body clocks, which can lead to a whole host of health issues.
While the occasional midnight snack won’t do much damage, you don’t want to make a habit of eating too close to bedtime or eating at night. But when exactly should you be done with your last meal?
Below, we’ll dive into the science of chrono-nutrition, or how when you eat can impact your health, as well as what and how much you eat. Plus, we’ll cover when you should stop eating to maximize good sleep and general health and well-being.
Eating a large meal may make you feel lethargic, but eating too close to bedtime can negatively impact your sleep in many ways.
Firstly, sitting or standing is a better position for digestion. When you lay down right after eating a meal, you’re increasing your risk of heartburn, indigestion, and gastrointestinal discomfort — and all three can easily keep you up at night.
When you eat, your body produces gastric acid so your stomach can digest food. This acid can travel up into your esophagus, giving you acid reflux. When you lay down shortly after eating, stomach acid can travel into your esophagus more easily than usual and stay there for longer, causing more pain and damage and keeping you awake.
And heartburn and acid reflux aren’t easy to treat. A survey by the Gallup Organization on behalf of the American Gastroenterological Association found that out of 1,000 adults who experience heartburn at least once a week, 79% said they get heartburn at night. Among those, 75% said it affected their sleep, and 40% said it impacted their ability to function the next day. Of those who took medication to try and help their heartburn, only 29% said this was extremely effective.
But it’s not just about heartburn and digestive issues. Your arousal threshold is lower after eating, meaning you’re more easily woken up even if you do manage to fall asleep after a meal. This makes you more vulnerable to other poor sleep hygiene behaviors like drinking coffee, exercising, or being exposed to bright light too late in the day, which can all disrupt your sleep, too.
Heads-up: Sleep hygiene is the name for the set of daily habits you can do to help you fall and stay asleep at night. Late-night eating is just one thing to look out for. The RISE app can guide you through 20+ sleep hygiene habits to help you get the sleep you need each night. RISE users on iOS 1.202 and above can click here to set up their 20+ in-app habit notifications.
Research shows high caloric food intake 30 to 60 minutes before bed may increase sleep latency (how long it takes to fall asleep) in women. And a 2021 study found eating or drinking an hour or less before bedtime increased the odds of waking up during the night.
And even if you can sleep soundly after a meal, the sleep you do get may not be as restorative as it could be. When we sleep, our brains clear out waste products. But, if your body is busy digesting a meal, blood gets diverted to the digestive system, leaving the brain with fewer resources to do this job.
So, all this is to say that eating too close to bedtime is a recipe for a bad night’s sleep. This might mean you:
Aim to be done with large meals two to three hours before bed to reduce the likelihood of all of this happening.
This goes for drinking in the evening, too. Obviously, anything with caffeine may keep you up, but alcohol can also fragment your sleep, or cause you to wake up during the night. Aim to have your last alcoholic drink three to four hours before bed. And drinking water too close to bedtime can lead to middle-of-the-night bathroom trips. Aim to stop drinking water two hours before bed. You can learn more about drinking water before bed here.
The RISE app can remind you when to finish eating for the day, as well as when to have your final coffee and alcoholic drink, all based on your individual body clock.
RISE users on iOS 1.202 and above can click here to set up personalized reminders to avoid large meals, caffeine, and alcohol.
Late-night eating can be a vicious circle. When you eat late at night, you can disrupt your sleep and cause sleep debt to build up.
Sleep debt is how much sleep you owe your body compared to your sleep need, which is the genetically determined amount of sleep you need. RISE can work out your individual sleep need, as well as how much sleep debt you’re carrying.
RISE users on iOS 1.202 and above can click here to view their sleep need.
RISE users on iOS 1.202 and above can click here to view their sleep debt.
When you have high sleep debt, the hunger hormone ghrelin rises and the satiety hormone leptin falls, meaning you get the urge to eat more in order to feel full.
Long term, too much late-night eating can lead to you overeating, gaining weight, and increased odds of obesity. Overweight individuals have a harder time falling asleep and staying asleep, and they also have a higher risk of sleep disorders like sleep apnea. These things can lead to higher sleep debt, which then leads to more hunger cravings and more weight gain. (And if you have sleep apnea, eating late may make symptoms worse, and may also increase your sleep latency, time awake during the night, and light sleep.)
Poor sleep is also linked to high cortisol levels in the evening, and these high cortisol levels increase blood glucose levels. This excess glucose can be stored as fat in the body, leading to weight gain and increasing the odds of obesity. And overweight individuals have a much harder time meeting their sleep need, creating another vicious circle.
What you eat is also important. One study found a diet low in fiber and high in saturated fat and sugar was associated with lighter, less restorative sleep and waking more often during the night. This’ll increase your odds of building up sleep debt, which can then lead to weight gain and further sleep disruption.
You can learn more about how sleep affects weight loss and food choices here.
As well as sleep disruption and weight gain, eating too close to bedtime has been shown to impact many other areas of your health and well-being, and many of them are caused by your body clocks being thrown out of whack, or desynchronized in science speak.
One key thing to be aware of here is your circadian rhythm. Your circadian rhythm is your internal biological clock. It runs on a roughly 24-hour cycle and dictates everything from your sleep-wake cycle to when your body produces certain hormones. But there’s more than one body clock to think about.
Your circadian rhythm is primarily controlled by a central pacemaker called the suprachiasmatic nucleus (SCN), which is found in the hypothalamus region of your brain. This is the master clock, but you also have body clocks in almost every organ system and tissue in your body — including in your digestive system.
These clocks are called peripheral clocks, and while your master body clock communicates with your peripheral clocks, they can all get out of sync with each other.
Zeitgebers are external cues that time your circadian rhythms to the outside world. Light is the most powerful zeitgeber, but eating can also change the timing of your body clocks.
Many of your body’s processes are dictated by the master clock in your brain. But others are controlled by meal timing. So, if your meal times don’t match the light-dark cycle of the outside world (which your master clock is following), your body will be getting mixed signals from the master clock and peripheral clocks, throwing your metabolic processes off.
Eating at odd times, like during the night or at very different times each day, can contribute to your body clocks getting out of sync. And this can lead to an increased risk of obesity and abdominal obesity, and many other health problems.
Circadian misalignment can also cause chronic inflammation, which can reduce how much energy your cells can produce, leading to low energy during the day.
The RISE app can predict your circadian rhythm each day and show you when your body naturally wants to wake up, go to sleep, and wind down for bed. You can then time your meals to match, avoiding eating in the evening wind-down and nighttime period.
RISE users on iOS 1.202 and above can click here to see their circadian rhythm on the Energy screen.
If you need another reason to keep meal times to during the day, research shows our circadian rhythm also controls oxidative stress, a close cousin and input to chronic inflammation.
Oxidative stress is when free radicals and antioxidants become unbalanced in your body. After eating, your body produces reactive oxygen species, a type of free radical, as it turns food into energy. Your body usually produces antioxidants to neutralize these free radicals and restore balance.
But this process is controlled by your circadian rhythm, which expects you to be eating during the day. If you eat late at night, those free radicals may not be neutralized, leading to oxidative stress. And oxidative stress has been linked to heart disease, Alzheimer’s disease, and cancer.
Badly timed meals can have surprising health impacts, too. One study found mice who ate during the day when they should be sleeping (mice are naturally nocturnal) got more skin damage when exposed to light. This is because the timing of an enzyme that repairs UV-damaged skin had shifted to be less active during the day.
Mice who only ate at night (their daytime), on the other hand, were less susceptible to skin damage from light.
While more research needs to be done to find out the effects in humans, one of the researchers, Dr. Joseph S. Takahashi said: “It is likely that if you have a normal eating schedule, then you will be better protected from UV during the daytime. If you have an abnormal eating schedule, that could cause a harmful shift in your skin clock, like it did in the mouse.”
Eating at night or late in the evening can change the timing of your peripheral clocks and cause misalignment between them and your master body clock. But the good news is, eating at the right time can help to keep all your body clocks working in sync with each other, and therefore has many health benefits.
When you eat only when you biologically should (during the day), you can help to maintain a strong circadian rhythm that keeps all your bodily processes happening at the right times. Our rhythms weaken as we age, so keeping meal times in sync with your body clock is even more important the older you get.
Eating at regular times each day can also help to keep your circadian rhythms in check. Irregular eating patterns have been linked to obesity, type 2 diabetes, and heart disease.
While there’s no one consensus on the best eating pattern, a 2019 review of studies on the topic concluded:
“From what we know, our best available research suggests that 3 meal-timing habits are likely important for good health:
Bonus tip: Late-night eating can also lead to weight gain and high blood sugar levels. You can learn more about what time you should stop eating to lose weight here.
If you can’t eat an earlier dinner, make doubly-sure to keep your sleep debt low. It may help protect you from the ill-effects of late-night eating.
A 2020 study looked at those who fasted during Ramadan. They ate one meal before the sun came up and another after the sun went down. The study suggested that getting a good night’s sleep, even when eating meals at these times, may help to keep your master and peripheral clocks in check, which would reduce the negative health impacts of misalignment.
Of course, not all of us can simply keep our meal times to the daytime. If you work night shifts, you’ll be up through the night and most likely want to eat during this time to keep you going at work.
Unfortunately, shift workers have been found to have a higher risk of diabetes, heart disease, and cancer. And the longer you’re in circadian misalignment for, the greater the risk of health issues. But, eating at the right times may help to reduce the impact chronic circadian misalignment has on your health.
A 2021 study found eating meals during the daytime, even when you’re awake at night, can keep body clocks in sync.
So, if you work night shifts, consider having a meal before and after your shift and not eating during the night shift itself. If you do need to eat, opt for light, healthy snacks instead of heavy meals. Eat fiber-rich complex carbohydrates to keep you full through your shift. And remember to try to keep your sleep debt low with excellent sleep hygiene.
You can learn more about sleep hygiene here.
Sometimes life gets in the way of an early dinner and you find yourself with an empty stomach come 10 p.m. If you do need to eat close to bedtime, opt for a light, healthy meal or snack such as:
Avoid fatty or fried foods or anything high in sugar or spice, which can cause acid reflux.
If you know a late dinner is coming up, try shifting your calorie intake to earlier in the day. Have a larger lunch and an afternoon snack, and then make your dinner more of a light snack than a main meal.
This advice also goes for those who find themselves waking up in the middle of the night with regular hunger pangs. Try eating a small, healthy pre-bedtime snack to keep hunger, and the sleep disruption it causes, at bay.
If you consistently get late-night hunger pangs, look at your meals throughout the day and make sure you’re eating enough at breakfast and lunch, and eating a balanced diet full of fruits, veggies, and complex carbs to keep you fuller for longer.
You can learn more about sleeping after eating here, including what types of foods to eat for better sleep.
There’s no set time you should stop eating before bed, but as a guide, you should aim to have your last meal two to three hours before going to sleep. Avoid late-night meals, late-night snacking, and nighttime eating as much as possible.
By keeping your eating to the daytime, and not during the late evening or night, you’ll be keeping all your body clocks in sync, reducing the chances of digestive issues keeping you up, minimizing health risks, and maximizing energy levels.
But remember, meal timing is just one piece of the puzzle. To really get a good night’s sleep, boost your health, and improve your energy levels, you need to think about everything from light exposure to exercise, and doing these at the right time, too.
It may sound like a lot, but it also means you can focus on light (guidance on this coming soon) and exercise timing (guidance on how to do this here) if you know you’ve got some late-night meals coming up.
To keep track of it all, the RISE app can tell you the best time to do all of these things each day based on your own circadian rhythm.
As a guideline, you should stop eating two to three hours before bed. This will give your body enough time to digest your food, lowering your chances of acid reflux and digestive issues keeping you up.
Eating before bed can lead to disrupted sleep, weight gain, and misaligned body clocks, which can lead to health problems like type 2 diabetes and heart disease. Aim to be done with your last meal two to three hours before going to sleep. You can learn more about sleeping after eating here.
If you’re hungry before bed, have a light, healthy snack like an apple and peanut butter, greek yogurt, or fresh fruit. Avoid fatty or fried foods or anything high in sugar or spice.
Avoid eating fatty, fried, or spicy foods, or foods high in sugar before bed. You should also avoid large meals and opt for a small snack instead. You can learn more about sleeping after eating here.
You should stop drinking water at least two hours before your target bedtime. This should reduce the chances of you waking up during the night needing to use the bathroom. You can learn more about drinking water before bed here.
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