The Incredible Things Your Body Does While You Sleep

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A look at the magical world happening behind your closed eyes.

Like many people, on most evenings I feel compelled to lie down for eight hours. As a child, I found this compulsion terrifying, to the point where I’d rather stay up all night rereading Enid Blyton adaptations of Greek tragedies than lose consciousness in (and possibly never return from) the weird world of sleep.

But if science has taught us anything, it’s how absolutely essential sleep is to learning, health, happiness and functioning as a human. Lack of sleep has been linked to everything from obesity to diabetes, cardiovascular disease, car crashes and global catastrophic events.

Clearly, your body is doing something right during that third of your lifetime you spend dozing. We look at some of the more wonderful things that happen while you sleep.

Your brain takes out the trash

Just like a computer with limited data, your brain needs to empty the trash once in a while so it can fit in more information. Scientists call this our glymphatic system, which is nearly 10 times more active when we’re asleep and basically works by flushing waste from our brain.

If this wasn’t terrifying enough, your brain cells actually shrink by 60 percent when you’re asleep, so there’s no way any unsaved files are sticking around. Some researchers compare the role of sleep as the equivalent of cleaning up after a party. You can’t entertain your guests and clean up at the same time, says Dr Maiken Nedergaard from the University of Rochester Medical Center study. Obviously he’s never hosted a warehouse party.

Your body heals itself

Asleep, your cells ramp up their production of proteins essential for cell growth, repair from stress and ultraviolet rays. Scientists have even found that sleep is vital to activate certain genes that help produce myelin, which is like insulation for your nerve cells. During the day, your body produces genes that try and kill those cells instead. Go figure.

You make memories

When you sleep your brain is busy consolidating memories, which is good news for those Broad City quotes you memorised earlier.


When your body sinks into a light sleep (that’s stage two from this infographic), your slowing brain waves are occasionally lit up with busts of rapid oscillations called sleep spindles, which can occur up to 1,000 times a night. While scientists are still figuring out exactly what these brain whirrs do, sleep spindles have already been shown to assist with building long-term memories and assisting our ability to learn.

Your brainwaves block out sound

Another amazing fact about sleep spindles (aside from the compelling alliteration) is they can help you stay asleep, even when your neighbours are slurring the lyrics to Dirty Old Town next door. A higher rate of spindles or brain activity has been associated with people who can literally sleep through anything, suggesting that your brain actually blocks noise to help you get a better sleep. People with fewer spindles are probably more likely to reach for those earplugs. Want to learn more about spindles? Budapest is hosting an International Conference on Sleep Spindling in May to discover more about these bad boys.

Your immune system bulks up

A rotten night’s sleep doesn’t just ruin your day, it’s also bad for your overall health. A bad sleep will even delay the effectiveness of vaccinations. Sleep helps maintain a healthy immune system, so it’s no wonder that when we’re overtired our bodies freak out, much like when we’re stressed.


Stress less with this picture of a sleeping puppy.

Your body secretly trims and tones

Another reason to love sleep even more is that it plays a big part in keeping your appetite under control, your weight down and your muscles toned. During sleep, the same growth hormone that got you through puberty helps you regulate fat and muscle mass as an adult – something body builders are already well aware of.

Sleep also helps regulate levels of the hormones ghrelin and leptin, which control how hungry or full you’re feeling. Leptin is basically kryptonite to carbs, so you can blame a lack of leptin for that entire loaf of bread you ate yesterday. When we’re sleep deprived, we feel like eating more, which is another reason why obesity has been linked to a lack of sleep.

You’re paralysed for a bit

In REM sleep, the beautiful dreamy state of the sleep cycle, your muscle groups become paralysed to stop you acting out your dreams. Sleep scientists call this atonia, and it’s pretty important because in this state your brain is active, your eyes are darting creepily from side to side, and let’s just say you’re probably not fit for company. When atonia doesn’t quite work, you can get some interesting phenomenon (or parasomnias) like sleepwalking. And when atonia works but your brain decides to awake, you get the horrifying mind-body mash-up that is sleep paralysis.


You keep learning

Not only does sleep improve your ability to learn while awake, it’s possible to keep learning even while you’re asleep. A Nature Neuroscience study taught sleepers to associate nice and not-so-nice smells with different tones, proving that even when asleep we’re pretty good at turning our noses up something we’ve learnt not to like.

Next time you embark on an all-nighter – be it for heading out partying or staying in for the latest Netflix jam – don’t complain when your body aches and groans the next day. Now you know that in those hours of shut-eye, your body is working its magic.

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Megan Anderson is a Melbourne-based freelance journalist and online editor for Going Down Swinging, who spent the last year writing her way around Europe. You can find her on Twitter here.