Dr. Matt Walker

last part of your night, wake up that sort of much later, 20, 25 minutes later, that's the REM sleep rich phase.

So if people go back and listen to episode one, we'll describe to you exactly how the different stages of sleep unfold across the night.

And they're not evenly distributed.

It's not as though you get just as much REM sleep as well as deep non-REM sleep in the first half of the night as you do in the second.

You get most of your deep sleep in the first half, and you get most of your REM sleep in the second half, and particularly in the last quarter of the night.

And this leads us to understand that the later into the morning hours that we go, the greater the hunger preference and the taste desire that is of your brain to start sampling from the finger buffet of all of those different stages, this thing called REM sleep.

And the later that you sleep into the morning, the more of that REM sleep that you will have.

And many people will have experienced this at the weekend, where they have this pattern that we don't recommend based on the QQRT.

QQR, regularity, go to bed at the same time, wake up at the same time.

What we see often in society is something that we call social jet lag, where you're short sleeping during the week, and then at the weekend...

you're out with friends or you're out sort of on the town, you go to bed late and you wake up late,

And maybe you're doing that by two hours.

Maybe you're normally in bed by 10 p.m.

during the week.

But now at the weekends, you're going to sleep maybe 12, 12.30, and you're waking up two, three hours later on a Saturday and Sunday.

And then the problem with that, parenthetically, is on Sunday evening, you've now got to go back to work the next day.

So you have to push yourself back to 10.30.

or 10 o'clock, whereas you were going to bed, let's say at 1 a.m.

on Friday and Saturday night, that's a three-hour time shift.

And people are doing that very frequently.