Most Replayed Moment: The Link Between Weight Gain and Sleep! Are Sleep Trackers Harmful Or Helpful?

0:00I love when a company takes something that everyone has accepted as being fixed and completely redesigns it, which is exactly what Lufthansa, today's sponsor, has done with its Lufthansa Allegro's Business Class cabin. It is stunning. Instead of having just one type of seat, Lufthansa Allegro's Business Class has five completely different seats, each engineered around a specific need. So there's one built purely around privacy, another with a bed that's over seven feet long, and one designed around having even more space to work, eat and think. You're essentially getting to choose what your journey needs to be before you even board the plane.

0:35And that level of thinking runs throughout the entire Lufthansa Allegris experience. An airline actually asking you, what does this traveler need from their flight? This idea that your seat should fit how you travel, not the other way around, is a surprisingly simple fix to something that the industry has never bothered to solve before. Anyway, it's called Lufthansa Allegris. And if you fly a lot, it's worth looking up. Visit Lufthansa.com and search for Allegris to learn more. That's spelled A-L-L-E-G-R-I-S. Lufthansa Allegris. All it takes is a yes. Limited availability on selected routes with more routes coming soon.

1:18You mentioned earlier that when people don't get enough sleep, the chance of obesity and weight gain increases. How does that happen? What's the mechanism? So there are probably many mechanisms, but one of the ones that is best understood is that we know that when you're sleep deprived, or indeed when your sleep is disrupted by anything else, like for example, sleep apnea, there are changes that occur in terms of hormone levels of of hormones that regulate our appetite and our satiety and so even a single night of sleep deprivation can result in a dramatic increase in your calorie intake overnight there have been some studies done for example in nurses so there was a study done that followed up nurses for 18 years and they looked at their weight and how much they slept on a regular basis and what they found is that those nurses that were sleeping less than about six hours a night on a regular basis, first of all, started off at the beginning of that 18-year period at a slightly higher weight.

2:24But over the course of those 18 years, they put on much more weight than other groups. So there is a very clear correlation between sleep duration, sleep quality, and weight gain. We see that, for example, in individuals who we treat with sleep apnea. So one of the treatments for sleep apnea is a mask-like device that you wear that stops your airway from closing down at night. And for some very overweight individuals, actually, when you treat their sleep apnea, they do manage to successfully lose weight, where in the past they found it absolutely impossible to do so. okay so if i'm underslept i'm more likely to eat more calories the next day yes am i also more likely to to reach for foods that are like high in sugar and bad for me certainly some studies do suggest that i think it's also important to say that sleep disruption or sleep deprivation has some fundamental effects for example on um your glucose tolerance so your insulin resistance um Which, of course, is a particular issue for people with diabetes, but it affects us all.

3:35So if you're very sleep deprived, there are changes to the way that not only your appetite or what you're reaching for, but also how your body processes the breakdown of those foodstuffs. Interesting. Because anecdotally, I think I can clearly say that if I'm underslept, I'm much more likely to eat something that is high in sugar or it's not good for me. We can all testify to that, can't we? You know, I think everybody has known that situation where they're very sleep deprived and they think, oh, well, I just need a bit of chocolate or, you know. What's going on in the brain there? Why is that?

4:12Is it something to do with the amygdala and the prefrontal cortex, the emotional center of our brain? Yeah, I don't think we know. I think it's probably to do with the reward mechanisms that underlie our behaviours, that there is something about sleep deprivation that alters the rewards that we're seeking. But I don't think I can give you a clear answer on that. You also talked about circadian rhythms. If I was a 10-year-old, what do I need to understand about the circadian rhythm, what it is, what it does, and why it's important? So within pretty much every cell of our bodies there is this 24-hour clock and in fact if you take a single cell and stick it in a petri dish about 40 % of the genes within that cell will exhibit this sort of 24-hour cycle and that 24-hour cycle really controls pretty much every biological system within our bodies be it how our liver works, how our heart works, how our lungs work there is one particular area of the brain called the suprachiasmatic nucleus that is viewed as the master clock it's the clock that coordinates all the other clocks within our within our bodies and that influences not only all of these other clocks that are occurring within the cells throughout our bodies but influences our behavior as well so influences generally speaking when we feel tired and when we want to go to bed and when we wake up and also influences things like you know when we feel most mentally alert when we want to eat when we want to drink when we feel most able to cope with work for example now that circadian rhythm that circadian clock for most people confers the sleep onset of somewhere between 10 p.m and midnight if you're an adult and waking up somewhere between 6 and 8 a.m.

6:10Now the timing of that body clock is governed by two things. It's governed by our genetics, so whether or not we are genetically predetermined to be slightly later in terms of our body clock or slightly earlier, and we see that in families where lots of people with, for example, will say, well, you know, I've always gone to bed late and woken up late but so has my father so has my grandfather etc etc but it's also influenced by what's happening in our environment about 50 percent of the definers of our circadian clock are governed by what's going on around us be that in terms of when we're exposed to light so we know that light is a very important driver of our circadian rhythm when we're eating when we're exercising when we're doing a whole range of other activities and also one of the markers of our circadian rhythm is the secretion of melatonin so there's a very small gland in the center of our brains called the pineal gland which secretes a hormone called melatonin that hormone tends to start being secreted in most people at around six o 'clock in the evening it peaks at the time that we want to go to sleep and then it starts dropping down a few hours before we wake up it's almost a a chemical marker of our circadian rhythm.

7:28But we also know that giving people melatonin in tablet form, for example, can influence our circadian rhythm. So there's this sort of feedback loop between our own body's secretion of melatonin and what our suprachiasmatic nucleus, our master clock, is doing. So by giving people melatonin at particular times of the day, we can shift your circadian rhythm forward or back. So that master clock in the brain, where is it positioned the supracasmatic nucleus is in a small area of the brain called the the hypothalamus and is that linked to the eye there are links from the back of the eye to the hypothalamus so there are some cells in the back of the eye in the retina that are not involved in vision not involved in conscious vision but what they are involved with is detecting blue light in particular which is the part of the spectrum of light that is most important in terms of regulating our circadian clock and there are direct links between these cells that are called retinal ganglion cells and the suprachiasmatic nucleus so exposure to light to blue light in particular is really very important in reinforcing or adjusting our circadian rhythm now of course we live in a in a world whereby the seasons change and the amount of light that we're exposed to changes so if we were on a set rhythm all the time that was immovable and unadjustable then there would be times where our circadian rhythm might not be uh might might be at odds with our environment so there does need to be some slight adjustment of that circadian rhythm and light is probably the most important adjuster blue light is that the light that comes from my smartphone uh so it's so blue light obviously the the strongest source of blue light is sun yeah um but yes these kinds of devices your smartphone your ipad in front of you a range of electronic devices also have blue light within them so so that's why if i'm if i'm up on my phone till 1am in the morning staring into the screen i'm kind of tricking that sort of optic nerve which is then impacting my master clock and i'm telling it that it's a different time yeah so so the thinking on that has changed a little bit over over the last year so it you know it was said that using these devices will trigger insomnia as of as a result of blue light actually it's likely that the amount of blue light that these devices put out is probably insufficient to do that directly but there are two effects of using your gadget until 1am the first is on a on a long-term basis if you're doing that regularly it will result in an adjustment of your circadian clock and push it back so you will want to go to bed a little bit later and wake up a little bit later which is fine if you're self-employed or you don't have any restrictions on your time but most of us need to be up at a certain time in the morning and if your circadian rhythm is delayed significantly the net effect of that is that you're going to end up sleep deprived i mean there's also the issue of being you know on twitter or being engrossed in a in a movie on netflix at 1 a.m that is going to make you delay sleep anyway so there are those two it's arousing it's arousing and it grips your attention well what do you make of these people i'm me being one of them that watch you know serial killer movies when we fall asleep well i think that that's only an issue if it's stopping you from falling asleep do you see because i have this argument a lot with my partner she she can't understand why i i need to watch this like really stimulating stuff when i fall asleep she likes quiet and i need to i tell myself i need to like listen to something do you see like variance in in this kind of thing and is there a better approach or this comes down to an individualized approach to sleep and that's why i'm always very reluctant to say this is the perfect night of sleep these are the rules for sleep you know for example there are some people who for whom caffeine doesn't really influence their sleep and can have a double espresso an hour before bed and still have no problems getting off to sleep for most of us that's not the case if you are somebody who can watch something very stimulating very scary and then switch it off and roll over and go off to sleep then i guess that's not a problem for you For most people, that's probably not the best thing to be doing at night.

11:55I think that long term, one of the issues is with all of these kinds of activities in bed at night before you go off to sleep is that they weaken the psychological associations between bed and sleep. and so if you start associating bed being a place where you're mentally active where you're engaged then if you have an underlying predisposition to insomnia for example then that can sometimes set the stage for developing insomnia later on the average person that you've treated worked with in your clinical practice that's struggling with sleep is at the heart of the issue just poor sort of sleep hygiene like you've said there yeah because Because I've got so many friends that say to me that they struggle with their sleep.

12:43Many of them have struggled with it for years. And I doubt that there's some sort of genetic reason why this many people are struggling with sleep. So I imagine it's just some kind of behavioral reason. So I think that the genes that predispose to insomnia are pretty widespread. But obviously, you know, in pretty much all areas of medicine, there is an interaction between genetics and environment. and certainly poor sleep hygiene and that's a horrible term i hate that term but it's the term that is most widely used and understood can certainly put in place certain aspects of behavior that then can give rise to chronic insomnia in the long term so if you've got very bad chronic insomnia then suddenly putting good sleep hygiene in place it's unlikely to fix it But it may be that that poor sleep hygiene in the first instance gave rise or at least predisposed you to developing insomnia.

13:41And what is poor sleep hygiene? If I wanted to be the worst possible sleeper in the world, what would I have to do? So I think you would probably have to set up your home office in your bedroom. Okay. You'd have to have, you know, your TV on in your bedroom all the time. Okay. Be surrounded by electronic devices. Drink a lot of coffee late in the evening. Alcohol? Drink a little bit of alcohol. So alcohol in the short term, of course, is quite sedating. It's a central nervous system depressant. But it does dramatically worsen the quality of your sleep, and for various reasons, the direct chemical effect, the fact that you've got a full bladder, the fact that you're probably snoring a little bit more.

14:26So alcohol's not a good thing. You know, not having a wind-down period. So, you know, gambling on the stock market until 1am, switching your laptop and then trying to go to bed, those kinds of things. So that's, you know, the quintessential very, very bad sleep hygiene. What about when I eat? So, you know, eating is perhaps less important, but avoiding a very large carbohydrate-rich meal before you go to bed for two reasons. One is that we know that it can cause some fluctuations in terms of your blood sugar. and also if you've got a bit of reflux it can make that much worse. Okay what about sleeping in bed with somebody else?

15:07Well I think that for some people they find again this goes back to no one rule for everybody you know if you've got a sleep trait termed sleep reactivity which is where your sleep is very liable to your environment then obviously sleeping next to somebody who's snoring loudly or who gets up in the middle of the night two or three times to urinate can be very disruptive to your sleep. If you've got very little sleep reactivity, you may actually find it comfortable, more comfortable to sleep with somebody in the same bed as you. I was thinking the other day, because where I've currently moved into, there's no blinds or curtains in my bedroom.

15:45And I was wondering if that might be a good thing. Because it at least means that in terms of my circadian rhythm, I'm waking up at the same time every day because I'm waking up when the sun comes up. Yeah but the sun comes up at different times on different days firstly so if you were doing that routinely you might find yourself really rather sleep deprived in the summer months and also there is some emerging evidence that exposure to light at night in your sleep is not very good for you so there was a very recent study that implied that light exposure at night increases your risk of diabetes so um it certainly is not good for the quality of your sleep and the likelihood is that you won't wake up as soon as it's light you'll wake up an hour or so after it's got light but during that hour or so it may have had a negative impact on the quality of your sleep so having a dark bedroom is really part of good sleep hygiene as is having a quiet bedroom that is not too hot or too cold what if you wear a sleep mask does that solve it yes it does i mean i wear a sleep mask i think it's you know particularly if you don't have good blackout curtains or blinds in your bedroom using a sleep mask particularly in the in the summer months is probably very helpful indeed does that mean that the only light receptors we have are behind our eyes well i think that there was a there were some rumors uh on the internet that there were um light receptors elsewhere but certainly the the only ones that we um know to be of significance in terms of defining our circadian rhythm are the ones in our retinas because i i did psychology when i was in uh secondary school and i remember reading one of the psychology books maybe my psychology teacher told me this i think it was mrs lowney that there were some studies where they shined a light like underneath someone's knees yes and people would like wake up when they shine the lights there i think that that's been that's been very much discounted now it is a bit strange though that the only light receptor would be behind the eyes it just feels like i don't know it feels like poor design that there's only one place where we figure out if it's night or day so so you know you see that for example in people who've lost their sight right So in some individuals who have lost their sight completely, then they lose the regulation of their circadian rhythm and they develop circadian rhythm disorders, something called a non-24-hour rhythm disorder, whereby their circadian rhythm is on, for example, a 25-hour cycle.

18:23And so every night they will go to bed one hour later than they did the previous night and will go right the way around the clock, you know, every month or so. So, you know, that's a very good piece of evidence that actually it's those cells in the retina that are of crucial importance for maintaining the stability of our circadian rhythm. I've read that down. I've read down in one recent study, 40 % of totally blind individuals had a non-24-hour circadian rhythm. Which really kind of for me also highlights just how important it is to think about my circadian rhythm and how much impact it's having on my whole body.

19:01The other part you mentioned was the biological element to our circadian rhythms, which people refer to as chronotypes. Yes. And this idea of chronotypes, which is essentially from my understanding that genetically we all have a slight sort of disposition to sleep at certain times and to wake up at certain times. Yeah. So there's these names, right? There's like the owl, the lark or whatever else. I think I'm an owl, but that also could just be bad habits. Yeah. So, you know, certainly there's that sort of genetic predisposition. There's also these environmental factors, but there's also age in that our circadian rhythm changes a little bit as we go through different stages of life.

19:41So, you know, it's not at all uncommon for teenagers to become more evening chronotypes. And then as we get older, we tend to shift back to the morning. So that's part and parcel of our aging biology as well. So I think that genetics is really important, but so are other factors as well. Studies in twins suggest that up to 50 % of our chronotype is under genetic control. So does that suggest that we are likely to have a similar chronotype to our family? We are likely to, but obviously our environment is not going to be exactly the same as our parents. what we do, our behaviours are not going to be identical to our parents or our siblings.

20:28So yes, we more frequently see that, for example, people have an evening chronotype that runs in families. But that doesn't mean that, you know, look, we're more than just the destiny of the genes that we hold. Obviously, our genes are really important, but so are other factors as well. If someone came to you and they said, I'm struggling with my sleep, you know, multiple nights in a row, I haven't been able to sleep, I'm getting in bed and nothing's happening. And then I'm waking up and I'm just sat there thinking about, you know, sleeping and I feel horrific. Where would you start? So I would start, I think, by trying to understand what it is that is causing their sleep issues.

21:11because a lot of the individuals that I see who have been referred in with that sort of picture assume that they've got insomnia and they may not always have insomnia so I think a key issue is that we are really really poor witnesses to our own sleep and what I mean by that is that we often our experience of sleep is very different to the reality of sleep when we bring in people into the sleep laboratory it's not at all unusual and I will almost always ask this question when I'm going through a sleep study with one of my patients is how much sleep do you think you got over the course of that night and it's not at all unusual for people to say to me well I think I've got two or three hours sleep occasionally even they say well I didn't sleep at all and then you look at their brain waves you look at the best objective marker that you've got of their sleep and you see that they've slept seven and a half, eight hours.

22:09So obviously what people are experiencing is really important because ultimately from my perspective, I want to improve people's experience of their sleep and what it is that they're complaining of. But it's important to understand that what they're telling you may not necessarily be the objective truth. Now that's really important when it comes to insomnia because it's not unusual for me to see individuals who, you know, they give you a story of very clear insomnia, but actually when you look at their sleep objectively, you find that although they say they haven't slept at all, they've slept seven hours, but that seven hours has been completely disrupted by conditions like periodic limb movement disorder, which is these leg kicks associated with restless leg syndrome, or sleep apnea, for example.

22:58Now, sometimes it's very evident from what people tell you that actually that's not the case that they've just got very clear insomnia so so that's really the starting point to try and decide whether or not you feel confident enough in your clinical evaluation of them that that you know what the issue is without doing a sleep study and if you think that they do need a sleep study then that's the point at which we we are we arrange for that it's also trying to understand some of the factors that might be driving their sleep difficulty so for example was their sleep were their sleep difficulties triggered by a life event did they have sleep reactivity before this insomnia started so were they one of those individuals who could sleep anywhere at any time whatever they wanted whenever they wanted to put their head down or were they kind of individual who the night before an exam before a job interview before a presentation would lose sleep because that often is a very strong marker for developing insomnia later on in life.

23:58And then it's also about trying to understand how the rest of their health is impacted by their sleep, but also how the rest of their health impacts on sleep. So it's not at all unusual for me to see individuals who have been started on medications for other reasons that have generated sleep issues, for example. You talked about this sort of obsession with sleep. And I was wondering, in the case of the patient you've just described, would you encourage them to wear a sleep tracker? So first of all I have to say that I'm not ideologically opposed to sleep trackers in general. I think that they are really really good for example in research.

24:37You know fantastic for research. It allows us to track sleep in very very large numbers of individuals and try and work out how that correlates with whatever we're interested in. One of the major issues with sleep trackers is that the people who often use sleep trackers are individuals who already are concerned about their sleep. So if you know that you're sleeping relatively little and you wake up feeling tired, then you probably know you're not sleeping enough. You don't necessarily need a sleep tracker to tell you that. If you're one of these individuals who has insomnia, who is spending plenty of time in bed, but simply cannot get the amount of sleep that they need, then what a sleep tracker will do is it will increase your concern, your anxiety around your sleep.

25:23It's a very different picture from, for example, using a step tracker. If you're sitting on the sofa and you look at your step tracker and you realize you've only done whatever it is, 5 ,000 steps, it's very easy to get up and go for a walk and do another 5 ,000 steps. If your sleep tracker is telling you you slept really badly and you know you slept really badly and you're already worried about how badly you sleep, there's nothing that you can do on the basis of the information that your sleep tracker is giving you to suddenly go and get a little bit more sleep. And it's complicated by the fact that sleep trackers are pretty good at telling you how much time you spent in bed.

26:00They're reasonably good at telling you how quickly you dropped off to sleep. The reliability, the accuracy of these devices, most of these devices, drops off significantly when it comes to, for example, defining nighttime awakenings, defining stages of sleep, those kinds of things. So then you have that additional issue in the mix, which is that sometimes your sleep tracker may be giving you information that is not factually correct, and that may increase your anxiety further. So I'm really very, very keen for people who have issues with their sleep, rather than just burning the candle at both ends, to put away their sleep tracker and actually go and have a chat with their GP or somebody who knows a little bit about sleep rather than relying on this sleep tracking technology do you think sleep trackers have had a negative or positive impact on sleep culture i think that for those individuals who can fix their sleep in a very straightforward way by spending more time in bed so the kinds of people that i talked about that 20 years ago would be saying well you know i only sleep five hours and you know because i'm busy doing x y and z and i can get away with it i I think it's probably encouraged them to spend a bit more time in bed because they know they have a very clear bit of information that's telling them that they're not sleeping enough.

27:23But for the people that I see, the people who are already concerned about their sleep and who have difficulties with their sleep, I think it's been a very negative impact. um and i have some reservations about well people like myself um sitting on these kinds of podcasts or writing in newspapers telling you well you know if you don't get enough sleep you're going to die early you're going to have all these negative health consequences because for a subgroup of individuals who are already very concerned about their sleep that actually can cause problems and i have seen individuals who for example have read books on sleep and how importance this is on sleep who have ended up going into a spiral of insomnia and very catastrophic depression and anxiety as a result so so it's very you know it's very important to be clear that all of this is a double-edged sword it's interesting with with sleep trackers um i can see i think it's worth me saying that i am both an investor in whoop and i'm also sponsored by week okay but i also agree with the things you've said so i've seen this this sort of variance in how a sleep tracker can improve some people's lives and it can make other people more anxious in a way that's not helpful so for me my sort of testimony on it is um i was one of those people you described earlier that thought sleep was take it or leave it and when i started seeing a sleep track, it's kind of like when I saw my brain for the first time, I did a brain scan and I didn't even kind of like realize it was there and that I could influence it and that things I was doing without really thinking much were having this big impact.

29:07And for me, what it did is it allowed me to finally make this link between how much sleep I've had and then how I behave. Now, I thought my behavior was random before, but seeing that when my sleep scores were down, I was way more emotional. I was way more likely to eat crap and the other thing that I saw which was really interesting was that when I had a glass of wine or two glasses of wine or three glasses of wine that it just like destroyed my sleep and I never knew that before and I was in search of reasons to quit alcohol anyway and when I saw that I quit alcohol forever so I've not drunk since so and then for me I have to also say there are moments in my life where life happens and I know I'm not going to sleep and I don't pay attention to my sleep tracker but there are other moments where I have a bit more control and that's when I kind of tune into my sleep tracker.

29:54I've also had parents message me a lot and say, listen, I've got a one-year-old, a two-year-old, a three-year-old, whatever. There's no point in me wearing a sleep tracker because, listen, I'm not going to get any sleep. And I also completely agree with them that there's really no point in that situation. I think there's a point when there's something you can do about it. Yeah, that's absolutely key. Yeah. So the point of doing anything like that is if there are very clear things that you can do on your own to close that loop there's no point having information without being able to act upon it yeah and i guess if you are one of those individuals like yourself who very clearly can correlate certain things that they're doing in their daytime lives with their sleep and and how they feel subsequently then then great you know i guess i have a little bit of bias in that the people that i see are already struggling with their sleep already and so it goes back i guess we're completely in agreement yeah we are yeah and it's so interesting because i that's been a developing idea because obviously my bias is always like wouldn't you rather know because that's you know but then from doing this podcast i've i've seen the comments and i've seen the struggle in from speaking to parents that struggling with their sleep and it's kind of sometimes just makes them feel worse about it um i think nuance is necessary on this issue what you just listened to was a most replayed moment from a previous episode if you want to listened to that full episode, I've linked it down below.

31:17Check the description. Thank you.

31:23I love when a company takes something that everyone has accepted as being fixed and completely redesigns it, which is exactly what Lufthansa, today's sponsor, has done with its Lufthansa Allegro's business class cabin. It is stunning. Instead of having just one type of seat, Lufthansa Allegro's business class has five completely different seats, each engineered around a specific need. So there's one built purely around privacy, another with a bed that's over seven feet long, and one designed around having even more space to work, eat, and think. You're essentially getting to choose what your journey needs to be before you even board the plane.

31:59And that level of thinking runs throughout the entire Lufthansa Allegris experience. An airline actually asking you, what does this traveler need from their flight? This idea that your seat should fit how you travel, not the other way around, is a surprisingly simple fix to something that the industry has never bothered to solve before. Anyway, it's called Lufthansa Allegris, and if you fly a lot, it's worth looking up. Visit lufthansa.com and search for Allegris to learn more. That's spelled A-L-L-E-G-R-I-S. Lufthansa Allegris. All it takes is a yes. Limited availability on selected routes with more routes coming soon.