It makes a kind of intuitive sense that eating just before going to bed is a bad idea. However, that might just be based on associations with compulsive late-night snacking or kebab-shop visits, because according to Registered Nutritionist Rob Hobson, who is working as an independent consultant for the Almond Board of California, eating just before bed isn’t necessarily bad for you.
“It depends on the individual,” says Hobson. “Some people have no problem sleeping and they’re a perfectly healthy bodyweight, and they can eat just before they go to bed.”
The problem with that kebab or bag of crisps in front of the TV might well be their nutritional content then, rather than the timing. Here’s Hobson with more information about how sleep is, and isn’t, affected by what you eat.
What foods and drinks can negatively affect your sleep?
You probably know alcohol is not brilliant. It’s a common sedative people self-medicate with and it really fragments sleep. It affects the REM part of your sleep cycle, which is the really restorative part of your sleep, and on top of that you may have to go to the bathroom in the middle of sleep or become dehydrated, which will keep you up. Spicy foods also aren’t going to do you any favours.
There’s also caffeine, which is likely to keep you awake. Some people are very sensitive to caffeine. You have a gene which determines how quickly you metabolise caffeine and if you’ve got a very slow metabolism for it, then you’re more likely to feel the effects even up to 12 hours later.
If you suffer from heartburn or indigestion then you should think about not just what you eat but when you eat. Very rich foods stay in the stomach for a while, resulting in stomach acid, which can exacerbate heartburn – a common reason why people can’t sleep.
Are there any foods that can help you sleep?
Tryptophan is an amino acid that is converted into serotonin in the brain, and that then makes melatonin, which is the sleep hormone. You find tryptophan in foods like turkey, seeds, nuts and oats. It’s quite hard for tryptophan to get to the brain because it has to compete with the other amino acids, but if you have that source of tryptophan with a source of carbohydrate it actually frees up the other amino acids, which are drawn to the muscle, leaving tryptophan to go to the brain to make more melatonin. You could have a chicken [which also contains tryptophan] stir-fry with some brown rice. Food combinations like that are the best way to get tryptophan to your brain.
Vitamin B6 and magnesium are other nutrients used to make melatonin. You get B6 in loads of foods like pulses, lentils, oily fish and meat. Foods that contain magnesium include nuts, seeds and dark green vegetables, and it’s really good because it also helps relax the body and the brain. It attaches to things called GABA receptors in your brain to quieten down the activity that causes anxiety in some people. So getting more magnesium could be good if you don’t sleep very well. And if you’re stressed the body loses magnesium very quickly, and stress is another reason why people can’t sleep, so you can get stuck in this cycle where you’re really stressed, losing magnesium, but then a lack of magnesium encourages insomnia and more anxiety.
What are circadian rhythms?
Circadian rhythms are a 24-hour cycle and they occur in all living beings. The sleep/wake cycle is just one example of a circadian rhythm. They govern the flow of hormones and biological processes to help keep us awake and help us sleep. The circadian rhythm is governed by your body clock, and your body clock is governed by light and temperature. If the light gets lower, your body produces melatonin and that gets you ready for sleep, and your body temperature drops. In the morning it gets light and your body stops producing melatonin, and it starts to produce cortisol and serotonin to wake you up for the day. Around that circadian rhythm other things happen around the day. We get a natural slump at about 2-3pm, which is why people feel a lack of energy then.
Can food alter your circadian rhythm?
It’s not that you alter it, but that nutrients in certain foods are involved in making melatonin. The important thing is to make sure you’re getting a well-balanced diet so you get enough of those nutrients to make the melatonin to help you sleep.
Really the best thing you can do if you struggle to sleep is to go to bed at the same time every night and wake up at the same time every day, because you’ll then be in sync with your circadian rhythm.
When should you eat last before going to bed?
It depends on the individual. Some people have no problem sleeping and they’re a perfectly healthy weight and they can eat just before they go to bed. You can keep a sleep diary to pinpoint the things that are keeping you awake, see if eating really close to bedtime does keep you awake for any reason, whether it’s heartburn or you just feel full.
Can when you eat affect your weight?
If you are worried about your bodyweight, you might not want to eat too early in the evening, because it will leave a big gap between eating and when you go to bed, which is a lot of time to snack. People sit in front of the TV, get the snacks out and start eating, because people tend to eat more in the evening.
People think that your metabolism slows down a lot when you sleep, so you shouldn’t eat too close to bed because it will make you overweight. It’s not really true. Your basal metabolic rate, which is the rate needed to survive, is the same throughout the day and night. Your body is really active at night, you have repairs going on throughout the body and your brain is very active processing memories. So in terms of bodyweight it doesn’t really make a difference if you eat just before you go to bed. There’s no real science to prove that, physiologically, eating just before you go to bed makes you overweight.
Can not getting enough sleep contribute to you becoming overweight?
There’s a thing called hedonic eating, which is about eating for pleasure, and there is research that people who don’t sleep well are more prone to it. You have a full meal then you still desire food, and you start eating sweets, chocolate, whatever it is.
There’s also research that shows that people who habitually sleep for less than six hours a night tend to have a higher BMI. It doesn’t mean than not sleeping will make you overweight, but it’s interesting – there’s something there in relation to the hormones that control appetite and hunger. You could find if you don’t sleep then you’re more hungry and less satisfied by the food you eat, according to this research. It’s not that it’s definitely linked, but it could be a causal factor in people being overweight.
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Nick Harris-Fry is a journalist who has been covering health and fitness since 2015. Nick is an avid runner, covering 70-110km a week, which gives him ample opportunity to test a wide range of running shoes and running gear. He is also the chief tester for fitness trackers and running watches, treadmills and exercise bikes, and workout headphones.