13 weird things your body does while you sleep

1. You lose weight

You’ve probably noticed you clock a lower weight when you step on the scales first thing. According to Michael Breus, PhD, author of The Sleep Doctor's Diet Plan: Lose Weight through Better Sleep, that’s because you lose water through perspiring and breathing out humid air during the night. Of course, this happens during the day too, but the effect is negated by eating and drinking. I can’t think of a better reason to get at least seven hours sleep per night! 

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2. As you fall asleep, you jerk

This happens to as many as 70 per cent of people and is totally normal. According to sleep experts, the size of the “hypnic jerk” reveals how sleepy you are, with some of us experiencing full-body spasms. The bigger the jerk, the more tired your body is. Weird.

3. You get taller

You don’t exactly shoot through the roof, but it turns out you gain height while you sleep. Why? “The discs in your spine that act as cushions between the bones rehydrate and get bigger, because the weight of your body isn’t pressing down on them,” explains Dr Breus. To boost this, opt for a firm mattress and sleep “on your side in the foetal position”. It’s worth a try!

4. Your body temp drops

When you’re active during the day, you burn more calories – but at night, your body temp lowers as a way to reduce the burn rate and save energy. Speaking to cosmopolitan.co.uk, sleep specialist and assistant clinical professor of medicine at UCLA School of Medicine Dr. Avi Ashaya says the phenomenon is a “survival mechanism… like how bears hibernate." Cool, huh? Your lowest temp occurs at about 2:30am.

5. Your blood pressure and heart rate decrease

When you’re sleeping, your body doesn’t need to work as hard or pump as much blood, so these systems slow right down. According to Dr Breus, it’s important for your cardiac muscle and circulatory system to “have time to relax and repair”, especially if you have high blood pressure to begin with.

6. Your eyes twitch

During REM (aka the deepest) sleep, your eyes dart from side to side. Scientists have no idea why – but they do know this is when your dreams are occurring. They also say it’s disconcerting to wake up during this deep sleep stage. 

7. You forget useless info

There’s a reason you can’t always remember everything that went on yesterday when you wake up. We take in so much information all day long, and there simply isn’t room for it in our brains. That’s why, according to sleep specialist Christopher Colwell at UCLA, a “sorting process takes place during sleep” – so you can forget the unimportant stuff. Like how much food you ate… 

8. Your body becomes paralysed

But your brain is at its most active! When you’re dreaming, your brain is more active than it is when you’re awake, meaning it requires more oxygen. Scientists aren’t too sure on the why: "One theory is that in REM sleep, you're organising thoughts and learning, filing information, but no one really understands specifically why a sleeping mind is active," says professor of neurology and director of UCLA's Sleep Disorders Center, Dr. Alon Y. Avidan.

9. You get sexually aroused 

You may already know men get erections while they’re asleep, but did you know women can become sexually stimulated, too? This has nothing to do with the sauciness of your dreams: it actually happens because your brain is more active, requiring more oxygen and therefore, increased blood flow all over the body. Medical sleep expert for SleepBetter.org says “there is natural clitoral engorgement because blood rushes to that area and causes swelling”. Interesting!

10. Collagen production amps up

Collagen strengthens blood vessels and gives skin its elasticity. When you’re asleep, you’re in a fasting stage, and a growth hormone is released. This stimulates collagen growth (yay), which is why, according to dermatologist Melanie Palm, “moisturising facial creams that contain retinols and retinoids are best to use before bed”. It ain’t called ‘beauty sleep’ for nothing!

11. Your immune system peaks

A recent study showed that people who got flu shots and were sleep-deprived the next night failed to create the antibodies needed to protect against the virus. The lesson? It’s so important to get extra zzz’s at the first sign of sickness. If you don’t, founder and director of the BlueSleep Center in New York City Dr. Jordan Stern says you risk becoming “chronically sleep-deprived” and hence “more likely to develop recurring infections”. No, thanks. 

12. You wake up continuously every hour

Between five and 15 times per hour, to be exact. This usually happens when you’re shifting to a different stage of sleep (such as from dreams to deep sleep). But don’t freak out if you can’t remember these awakenings – most of them are so brief, they’re instantly forgotten.  

13. You stop breathing

Up to 30 per cent of people actually stop breathing at one point during the night. The disorder, sleep apnea, often goes undiagnosed. Dr. Stern’s advice? “If you or your partner snores at night, it’s time to get checked out”. Noted. 

Did you know about any of these weird sleep scenarios?