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

Steven Bartlett (0:00)

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You 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?

Dr. Guy Leschziner (1:29)

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 hormones that regulate our appetite and our satiety. So even a single night of sleep deprivation can result in 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 slightly higher weight, but 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.

Steven Bartlett (3:04)

Okay, so if I'm under-slept, I'm more likely to eat more calories the next day.

Dr. Guy Leschziner (3:10)

Yes.

Steven Bartlett (3:10)

Am I also more likely to reach for foods that are like high in sugar and bad for me?

Dr. Guy Leschziner (3:16)

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 your glucose tolerance, so your insulin resistance, which of course is a particular issue for people with diabetes, but it affects us all. So 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 food stuffs.

Steven Bartlett (3:48)

Interesting. Because I anecdotally, I think I can clearly say that if I'm under-slept, I'm much more likely to eat something that is high in sugar or-

Dr. Guy Leschziner (3:59)

Well, I think we can all testify to that, can't we? 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-

Steven Bartlett (4:10)

What's going on in the brain there? Is it something to do with the amygdala and the prefrontal cortex, like the emotional center of our brain and the-

Dr. Guy Leschziner (4:17)

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.

Steven Bartlett (4:37)

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.