What Happens to Your Body When You Sleep

A regional survey found that Malaysians only sleep an average of 6.4 hours – 1.6 hours short of the recommended eight hours. So why is this important? Here’s what happens to your body when you sleep.

Your body temperature drops

Body temperature will drop gradually during the night, along with hormones like adrenaline as you’re not as active as you were during the day. When your body temperature is lower, you’re more likely to have better, deeper sleep because it gives your body a chance to rest and rejuvenate. This is why most of us sleep better in an air-conditioned room – the higher your body temperature, the harder it is to stay in deep sleep.


Your body becomes paralysed

Sleep is categorised into rapid eye movement (REM) sleep (light sleep) and non-rapid eye movement (NREM) sleep (deep sleep). Each sleep cycle is about 90 minutes and you start off by drifting into NREM, usually accompanied by jerks right before deep sleep sets in. Towards the end of the sleep cycle, in REM sleep, your eyes move back and forth, heart rate becomes irregular, and muscles are paralysed to protect you from acting out vivid dreams. At the end of the 90-minute sleep cycle, you come to a brief awakening and readjust your body position before falling back asleep.


Your brain processes information

Sleep is the time when your brain downloads everything that you learnt during the day, organising and storing them as either short-term or long-term memories. Any information that you don’t need is filtered out, which is one reason your mind is clearer after a good night’s sleep.


Your organs get repaired

At about seven to nine at night, your kidneys and bladder slow down for repair. From nine to 11pm, you’ll start getting tired and weak as your blood vessels and arteries are in intensive repair mode. From 11 to three in the morning, you might find it difficult to fall asleep, mainly because body wastes are not being processed by your liver, causing them to act as irritants. At about three in the morning, your lungs begin to diffuse gaseous waste and you might find yourself coughing in the middle of the night. Slightly before dawn at five, it’s time for your colon to flush away body wastes – it needs plenty of water to be at its best, so going to bed well hydrated is important.


Your appetite is regulated

When you have a large sleep debt, you might have more cravings for fatty food during the day. Melatonin, the hormone responsible for making you feel sleepy and regulating your body clock, also factors into your ‘hunger clock’. Research shows that sleep deprivation throws off melatonin production, which in turn influences the production of hunger-regulating hormones such as leptin and ghrelin. Less sleep means you could gain more weight!


Expert: Sarah Harris Ong, sleep coach at Sleep Champ Baby