So I think it's pretty clear that sleep restriction, poor sleep, does cause dysfunctional metabolism. And so the question is, can you fix your sleep and improve metabolic health? So there's a couple of evidence-based ways we're going to talk about improving sleep. Both of them involve good sleep hygiene. So good sleep hygiene is really the foundation of good sleep. And there's a variety of factors that are like a checklist of it. I didn’t include all of them, but some of the main ones here are using light smartly. So bright light exposure first thing in the morning, at least 30 minutes, is one of the most important ways to reset your circadian rhythm so that you become sleepy at a normal time.

Very, very important for resetting circadian rhythm and also important for stopping that melatonin production when you're first waking up. Also, avoiding bright light, blue light exposure in the evening after sunset. Blue light is what is inhibiting melatonin production in our eyes. It's through our eyes, actually, not in our eyes. But it's inhibiting melanopsin, which then is involved in the signaling of producing melatonin to make us sleepy. And so you want to avoid blue light either by having light dimmers or different color lights, maybe red or orange. Also glasses you can wear to filter it out. But also realize that screens are full of bright light, blue light as well. So turning down the screens, maybe avoiding screens at night is another good idea.

Also making sure your room is dark because there have been studies showing that even a little bit of ambient light coming in disrupts sleep. Managing temperature is important. So part of what melatonin is doing besides making you sleepy is it's lowering your core body temperature. And this is part of the circadian rhythm. It's important. Important for good sleep. And so you want to make sure you're not sleeping in a really hot room. And there's many ways that you can obviously maintain your bedroom temperature. Optimizing meal timing is also important. So in addition to the importance of avoiding eating 3 hours before your bedtime because of the melatonin production, it also improves your sleep. So this has actually been some work by Dr. Satchin Panda at the Salk Institute as well.

He's identified from large studies that he's done that people that stop eating 3 hours, at least 3 hours before their bedtime, sleep better. And that's also partially because you're not digesting. I mean, digesting is an energy-consuming process that's happening while you sleep. So it makes sense that it would also disrupt sleep somewhat. Regular exercise. So again, these are all tied together. So the exercise is also a very powerful zeitgeber. So just routine exercise is also really important for resetting the circadian rhythm and helping you just get on that rhythm and go to bed at a normal time. And then monitoring caffeine intake. Caffeine shifts the circadian clock by 45 minutes. So if you're drinking a cup of coffee, that's 45 minutes of a circadian shift.

And then you have another cup of coffee. That's 45 minutes of a circadian shift. And so you're going to be going to bed hours later if you're drinking 4 cups of coffee, particularly if it's afternoon. Obviously, there's a lot of individual variation between the way we metabolize caffeine. So yeah, there's some individual variation. But generally speaking, it still shifts circadian rhythm by about close to an hour. So sleep extension is one of the evidence-based ways that's been shown to improve sleep. And this involves really just adjusting your bedtimes to increase the sleep time. So either going to bed earlier or sleeping in both of those. It also involves a lot of consultations with sleep experts and then sleep hygiene recommendations like we just discussed.

And so there's been meta-analyses looking at sleep extension in people that are short sleepers. So they're getting fewer than 7 hours of sleep per night. And when they undergo this type of behavioral change, when they're engaged in sleep extension, for every hour additional that they're sleeping per night, they improve their insulin sensitivity, regardless of their body weight. They improve and normalize their hormones, leptin and ghrelin. They have reduced appetite. They're not getting so hungry. Their sugar intake goes down. And their caloric intake goes down. And they lose weight.

So all these things, of course, the sugar intake and reducing the calories, it's all regulated by the satiety hormones, which again, if you're increasing your sleep, you can basically flip that switch to help regulate them back and normalize them back. The other type of evidence-based way of improving sleep is a certain type of cognitive behavioral therapy for insomnia, CBT-I. This is probably one of the most used, well-known, and effective ways to improve insomnia. It involves a variety of factors I'm not going to go in depth on, but stimulus control is the main one. So that means the bed is only associated with sleep. So no watching TV in your bed, no scrolling on your phone, no doing anything screens in your bed. Bed is for sleeping only. So that's stimulus control.

It involves sleep restriction, which is a little ironic, paradoxical. But so that means if you're laying in your bed and you're tossing and turning and you're up for an hour or 2 or 3, it means getting out of your bed and going into another room, dark room, like your living room couch, and lying there. And you do some relaxation techniques that you learn about. And then wait till you get sleepy and then go back into the bed. So again, bed is for sleep only. It also involves implementing a variety of the sleep hygiene factors that we talked about, sleep education, and again, some relaxation techniques. So meta-analyses of CBT-I have also been shown to improve metabolic health in people with insomnia, including improved HbA1c, improved blood pressure.

Of course, their sleep quality and insomnia factors and all those things improve as well. So it's pretty clear that people that have poor sleep, that have insomnia, that are short sleepers, if they work on fixing their sleep, they improve their metabolic health.