Dear Dr Adam,
I often come home from work late and eat a meal around 10 pm. What implications is late-night eating having on my sleep and overall health?
Well, my first question to you is how soon after that meal are you going to attempt to go to bed?
If you have a large meal just before you sleep, this can be disruptive to sleep because of the digestion cost and the discomfort it can cause. If you’re digesting a big meal, it’s quite a big effort to digest it – the fact that people report feeling uncomfortable after a particularly large meal is not simply coincidence.
The other bigger aspect that people are now looking at, though, is Chrono-nutrition – the practice of efficiently timing when you eat. As an example, if you think of having something large to eat very late at night, that meal falls at the end of your active period. You’re not really geared up metabolically to cope with that meal then because the time it takes to clear from the system is longer than it would be earlier in the day. If you were to have the same meal for breakfast, though, you’d be more primed to digest and absorb the fuel you’ve taken on board.
On a more basic level, if you have a big meal at the beginning of the day, that then acts as fuel for the period that follows because you’re using energy during your active period. If you have it at the end of the day, you’re getting an influx of this fuel that takes longer to clear from the system, coupled to the fact that you’re inactive and not demanding any fuel.
So is it bad for you to be eating at this time? Well, if you look at the literature – yes, it would be worse to have that meal at 10 pm than 10 am.
But it’s not uncommon for people to energy load late in the day because, of course, people are working, travelling to and from work, doing other things outside of work, and so the opportunity to eat often isn’t available until this time. Given that, what can we do to mitigate against it?
“In this country, we used to get most of our fuel in the middle of the day, and in Mediterranean countries, they still tend to have their big meals at lunchtime or the afternoon rather than late at night”
Yes, we could have breakfast like a king, lunch like a prince, dinner like a pauper – as we used to do. In this country, we used to get most of our fuel in the middle of the day, and in Mediterranean countries, they still tend to have their big meals at lunchtime rather than late at night.
However that’s not to say they’re not eating anything late at night – often it’s actually later than we are – but the energy distribution is different. And even then, Mediterranean’s tend to go to bed later and they space that meal out over a longer period of time. It’s a lifestyle; not just the composition of what you’re eating but how you’re eating it, sitting down at a table with your family, spreading that meal out over a couple of hours rather than shovelling it in your face as quickly as you can, which happens to be 10 at night.
But going back to how we can mitigate, let’s say we haven’t got the luxury of being able to live like a Mediterranean and go home at lunchtime to have a three-hour siesta, relax with family, then go back to work. The other way you can manage it is to look at the rest of the meals in your day.
If you have a big meal at 10 pm one night and you wake up at 7 am the next morning, you might want to refrain from eating or look more carefully at what you’re eating around that time, You could push your breakfast to later to extend the fast and give yourself extra time to clear what you had the night before from your system. In doing this, you’re effectively moving your eating window to later, starting later and finishing later.
When you look at shift workers – which is where a lot of the evidence comes from that eating late at night is worse for you – the overriding issue is that you have a double-whammy of eating in the middle of the night, but not doing it consistently. Instead, they do it for maybe two days a week and for the rest of the week they eat in a normal pattern. So they’re eating at the wrong times of day not consistently, but intermittently or for a short period of time.
That’s where new evidence comes in about how you can train your body to be better able to cope with eating at a particular time of day. It might be against your central circadian rhythm, but if you’re doing that meal pattern late at night all the time, then your gut can be trained to cope with it and get accustomed to that time frame.
“It’s almost in our psyche that we can’t go longer than an hour without having something to eat or drink, grabbing a coffee here or a croissant there. We’ve been brought up in a culture where we have a constant grazing habit”
The problem with society today, though, is that we eat all the time. It’s not just that we’re having a big meal after 10 pm; we’re eating consistently from 7 am right the way through to midnight – snacks, drinks and meals combined. It’s almost in our psyche that we can’t go longer than an hour without having something to eat or drink, grabbing a coffee here or a croissant there. We’ve been brought up in a culture where we have a constant grazing habit.
So, if you’re having these 10 pm meals, the best advice I can give is to be mindful of what you’re going to eat the following day. If you know you’re going to eat lots at the end of the day, maybe don’t have any recognised breakfast, or push breakfast to later in the morning, or get rid of that frappuccino you’re having on the way to work and replace it with a water or tea – something that doesn’t give you a calorie load.
So is there any truth in the feeling of tiredness after a large meal, or that eating can aid sleep?
There are reasons for this. First and foremost, we often overlook the energy cost of digestion. When you have a large meal – particularly if it was a rich meal – it takes a lot of effort to digest and absorb it.
That manifests as heat; you might even feel your belly become warm or start to feel hotter overall. What’s happening is known as diet-induced thermogenesis – the thermic effect of feeding – which represents all the energy it took up to digest that food, break down and synthesize proteins, move the gut around to churn that food, secrete liquid and enzymes into the gut. You then have to actively use energy to transport the digestive products of that food through the gut wall and into the blood. All that contributes to a drain of energy which makes people feel tired.
The other thing that often happens – particularly if you have a large carbohydrate load in that meal – is that you produce a lot of insulin. You might overproduce insulin and consequently absorb more sugar from the blood than you’ve imported, translating to a slight dip in blood glucose, which is the fuel your brain uses, and so this might contribute to feelings of tiredness.
But while a large meal might make you feel sleepy, the quality of the sleep you’re going to get is still compromised. You’re going to fall asleep with all that food still in your gut, still digesting and absorbing, and it’ll take you around eight hours to clear that food from your system. As dawn breaks, you probably still have remnants of the meal from the night before in your blood.
It’ll also dehydrate you. When you digest a lot of food, you draw liquid out of the body. So yes, you might fall asleep, but you’ll likely wake up in the middle of the night to get a glass of water, or go to the toilet in the same way as if you’ve gone to bed having lots of alcohol. You’ll collapse as though you’re comatose, have a rubbish night’s sleep and feel terrible the next day.
To have your nutrition questions answered by Dr Adam Collins, please email firstname.lastname@example.org/us