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Welcome to feel better, live more bite size, your weekly dose of positivity and optimism to get you ready for the weekend. Today's clip is from episode 26 of the podcast with world leading sleep researcher and professor of neuroscience and psychology, Matthew Walker. In this clip, Matty shares research on the importance of sleep for our overall health and the amazing power it has to recharge our mind and body. You make a very powerful case why sleep is the foundational pillar of health.
Yeah, you know, I used to think that sleep may be the third pillar of good health alongside diet and exercise, but the more I sort of did my research and the more I read from other people, I realized I was probably wrong that in fact sleep is the foundation on which those two other things sit. And I'll give you an example in each, firstly for diet and exercise. We know that if people are trying to lose weight and they're being judicious about their food intake, they're trying to diet, but they're not getting sufficient sleep. 70% of all the weight that they lose will come from lean muscle mass and not fat, because your body becomes very stingy in giving up its fat when you are under slept.
So dieting becomes quite redundant in that regard, you know, you want to keep the muscle, you want to let go of the fat and sleep deprivation will do the opposite to you. We know that without sufficient sleep, two critical appetite hormones go in opposite bad directions. One of those hormones is called leptin, which is a hormone that signals to your body your full, you don't want to eat anymore. The other hormone is called ghrelin, which is the opposite, it says you're not satisfied with your food, you want to eat more and despite leptin and ghrelin sounding like two hobbits, they are actually real hormones.
What's interesting is that when you sleep deprive people or even just limit them to maybe just like five or six hours of sleep for a week, levels of leptin, which say your full don't eat more, they drop down, levels of ghrelin that ramp up your hunger and say, I just eat in a big meal, but I'm not satisfied. I want to eat more that hormone skyrockets when you're under slept. So no wonder people who are sleeping just five to six hours a night will actually eat on average somewhere between two to three hundred extra calories every single day. Yeah.
So you can solve sleep and you will actually start to not want to eat as much, but let me move over to activity we spoke about the foundation on which diet sits. When you are not sleeping sufficient amounts, firstly, the likelihood that you will actually exercise decreases significantly, your motivation to be physically active drops away. Even if you are physically active, the intensity of your workout will not be as strong, so it's less effective and less efficient. Things like your vertical jump height, your muscle contraction strength, even the exchange of carbon dioxide and oxygen in your respiratory systems, they get worse when you haven't slept.
The beauty of that part of the relationship and the same for diet is that it's bi-directional, that if you actually improve your sleep, you can improve those two things, but conversely, those two things will improve sleep. So if you start to correct your diet, you start to sleep better, but physical activity is a great way to enhance both the quality and the quantity of your deep sleep. I often say this when I'm teaching doctors, why are we not bringing up sleep quality with pretty much every single patient that walks in through our door? Sleep really is the tide that raises all of the other health boats.
It's the superordinate node that if you manipulate it, it's like the Archimedes lever, you pull that, everything else can start to come into play. You get the sleep and it affects your brain, affects your hormones, affects your genetic expression, it affects all these sort of things that we might be looking for drugs to affect those individual pathways, but you can improve a lot of them by improving your sleep. We think, well, that sounds almost too good, but don't forget, it took more than age of 3.6 million years to evolve this necessity of eight hours of sleep in place, which I should know, by the way, that if you look at the data back in the 1940s, the average adult was sleeping about 7.9 hours of sleep. Now that number here in the United Kingdom was closer to 6 hours and 30 minutes.
In other words, within the space of 100 years, which is a blink of an evolutionary eye, we've locked up almost 20% of our sleep need. In medicine, often or even in research and pharmaceuticals, we're often trying to manipulate one pathway in one area of the metabolic system, one one aspect of the immune system, or one feature of the cardiovascular system, and sleep affects all of those, and you speak a lot about the immune system, it's so key for our health. So what does sleep do for the immune system? So firstly, we can look on both sides of the coin, what happens when we don't get enough sleep?
Firstly, we know that people who are sleeping in five hours a night are four times more likely to catch a cold than those people who are sleeping eight hours on one striking study, very well controlled study. We also know that it doesn't take one week of short sleep deprivation, one night is enough. What we've found is that if you take healthy individuals and then we limit them to just four hours of sleep for one single night, what we see is a 70% drop in critical anti-cancer fighting immune cells called natural killer cells, which are these wonderful sort of immune assassins that help decrease our cancer risk and help us fight infection in foreign immune system. Exactly.
Part of that critical innate immune response flipped the sort of the side of the coin, and now what we find is that when you get sleep, there is a change in what we call the autonomic nervous system, which is sort of this automatic part of our nervous system, and that automatic nervous system is split into two branches, one that is sort of like the accelerator pedal that gets us revved up, triggers the fight or flight response, the other is the brake, that sort of calms us down. And when we go into deep sleep, we apply that brake to the nervous system and everything quiets down. Heart rate decreases. Deep sleep is the most wonderful form of natural blood pressure medication that you can ever wish for.
But one of the other things is that we see as that nervous system quiets down levels of things like cortisol drop down, that stress-related chemical, and it's during that time that the body goes into an immune stimulation mode, and it's where essentially you're going to restock the armament of your immune army so that when you wake up the next day, you can battle and fight infection. What's also fascinating, I love this data, and this tells you just how critical sleep is to fighting for our health. If you look at people who become infected or you actually infect them in the experimental laboratory, let's say with sort of a cold vaccine, or you immediately trigger increased sleepiness and increased amounts of deep sleep, and it turns out that the infection indicates to the immune system that you're under attack, and the immune system will actually signal to the sleep system within the brain, we need more sleep. Sleep is the best battle force that we have right now to combat this assault.
And so that's why when you're sick, all you tend to want to do is just curl up in bed and go to sleep. The reason is because your body is trying to sleep you well. It's an appropriate response to what's going on. Exactly.
The bodies are pretty clever, right? They are remarkably clever. You know, again, mother nature has figured this out. And so she brings up this thing called sleep, which I would argue is probably like the Swiss army knife of health.
You know, whatever ailment you are facing, it is more than likely that sleep has a tool in the box to try and help fight it. That's so cute. Whatever ailment you're facing, guys, if you're listening to this, whatever you're suffering from, whether it's lack of energy on a day-to-day basis, whether it's that you're worried about your risk of developing a chronic disease such as types of diabetes or heart problems as you get older, you know, what Matthew was saying, what Professor Walker was saying is that sleep, improving your quality of sleep, is going to help you with all these different facets. It's going to help reduce your risk, it's going to help increase your energy.
It's also going to reduce your risk of actually getting disease in the future, which is absolutely incredible. In your experience, what are those common things that people aren't doing that they could do to help improve their sleep? The first is regularity, going to bed at the same time and waking up at the same time, no matter what. Even if you've had a bad night of sleep, still try to wake up at the same time, just understand it's going to be a tough next day, and then get to bed at the same time that following night and you'll have a good night of sleep, you'll sleep a little bit more soundly that night.
Even if it's the weekday or the weekend, don't do so what we call social jet lag, which is sort of where you sleep too late at the weekend, and then on Sunday night you've got to drag your body clock all the way back and try and force it to sleep at a time when you haven't been sleeping before. That's torture. Regularity is key. The second thing is temperature, keep your bedroom cool, and probably around about 18 degrees Celsius, which is called to the most people think, but cooling the room down takes your body into that right sort of thermal space for good sleep.
It cools it down. We are, I think, a dark and deprived society in this modern era, and you need darkness at night to allow the release of a hormone called melatonin, which helps time the healthy onset of your sleep. So, yes, it's to do with blue light, sort of emitting devices, screens, phones, those are things that you should try and stay away from in the last hour before bed, but it's not just that. It's also overhead lighting.
We don't need to be bathed in an electric light all night. In the last hour before bed, just try turning half of the lights off. You'd be surprised at how soparific and sleepy you become when you're shrouded in darkness. So, that's the third thing.
The fourth thing is, I would say, walk it out. And what I mean by that is, don't stay in bed if you've been awake for 20 or 25 minutes, either trying to fall asleep or you've woken up and you're trying to get back to sleep. The reason is because your brain is this wonderfully associative device, and it will start to very quickly learn that being in bed is about being awake rather than asleep. So, what you need to do is, after about 25 minutes, just relax, understand that sleep is not quite here yet, go to a different room in dim light, read a book, or listen to a podcast, only return to bed when you are very sleepy.
And that way your brain will start to relearn the association that your bedroom is the place of sleep. Matthew, thanks. I love that. Let's go into caffeine.
How much of a sleep disrupts is caffeine? If you have a cup of coffee at noon, a quarter of that caffeine is still circulating around your brain at midnight. So, to put that in context, it would be the equivalent of getting into bed and just before you turn the light out, you swing a quarter of a cup of Starbucks and you hope for a good night of sleep. You know, you would never do that because, you know, but that's exactly unfortunately what people do, you know, completely innocently by drinking caffeine, you know, still too late in the afternoon.
You know, we often don't think about the implications of that and so many patients of mine tell me that, oh, you know, if caffeine can be a problem for some people, I'm not one of those caffeine is fine for me, but more often than not when they either reduce their intake or cut it out completely, the sleep quality goes up. And this is one thing I just want to end on is just to say, guys, look, it may not be that you can just change for one thing and suddenly have a great night, so you might have to change three or four things together. You know, that certainly might experience this, like, you might try, for example, one week with no caffeine and no alcohol and see how you sleep because then you can be empowered to decide what you're going to do after that. I always try and get people sleeping as well as they've ever slept and then they can start reintroducing some of these lifestyle things that they want and they can say, oh, wow, that's interesting.
I felt great last week, but now when I have a 2 p.m. coffee, you know, I'm not quite as good. Okay, that's that's going to teach me now that I'm going to knock it a bit early in the day because I think ultimately nobody's going to follow your advice or my advice simply because we told them to. I think it's only when they start to feel the difference themselves.
They go, you know, I kind of like feeling it. Hope you enjoyed that bite size clip. Please do spread the love by sharing this episode with your friends and family. And if you want more, want to go back and listen to the full conversation with my guest.
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