You Never Knew Your Body Does These Things While You’re Asleep

On your busiest, most stressful days, you probably look forward to crawling right back into your bed by noon. There’s just nothing that feels quite as restorative as getting a good night’s rest. You awake refreshed, energized, and ready to take on all the tasks that seemed so impossible just yesterday.

You might even have a general idea of what happens during your nightly slumber — you’re aware some dreaming is involved and you’re semi-conscious for part of the time. But do you really know what’s going down inside your body? Here are a few things that happen while sleeping you aren’t even aware of.

1. You lose weight

Doubtful Woman Adjusting Weight Scale

Don’t get too excited about a low number on the scale in the morning. |

You know by now jumping on the scale first thing in the morning is the way to go — it’s when you typically weigh the least, after all. But you shouldn’t get too excited. The weight loss associated with sleep is mostly just water, says With each breath you take while you’re asleep, you emit water vapor that can contribute to a lower weight. And Derek Muller, a physics teacher, told NPR you lose a lot of carbon dioxide when you sleep, thus resulting in up to a pound of weight loss. You probably wish that morning scale number would stay where it is, but unfortunately, it creeps back up during the day.

2. Your muscles are paralyzed

Man sleeping in his bed

There’s a reason you don’t physically move even during your scariest dreams. |

Even during your most vivid dreams, there’s a reason your body stays still as your mind runs wild. Daniel A. Barone, M.D., tells Prevention the only muscles that move during REM sleep (the deep sleep stage when dreams occur) are the ones that control your eyes. It’s not permanent, of course, and REM sleep only lasts for about 20 minutes. But during this time, the rest of your body is pretty much paralyzed without you even realizing it.

Most of us never consider how our muscles temporarily stop functioning, but there are the unlucky few with sleep paralysis. If you have this condition, you’ll experience a sensation of being awake but still not being able to move your body, WebMD explains. It can happen as you’re falling asleep or as you’re waking up, and is reportedly very frightening.

3. Your eyes move — a lot

Close-up of beautiful woman with eyes closed

It’s called rapid eye movement for a reason. |

That deep sleep stage known as REM isn’t called rapid eye movement for no reason — it’s really the stage when your eyes dart back and forth. Live Science reports scientists theorize your eyes move like this during this stage of sleep because you’re watching the images in your dreams. Thanks to a study in the journal Nature Communications, this idea may finally be proven.

Nineteen people had their brain activity recorded while they slept, and researchers found the participants’ medial temporal lobes lit up with activity while they were in REM sleep. This is the same part of the brain that’s active when you’re looking at pictures of famous people or things. And medial temporal lobe activity is associated with rapid eye movements whether you’re asleep or not. It’s a small study, of course, but it’s pretty interesting.

4. Your throat narrows

man holding a baby and sleeping

If you snore, your throat might become more narrow than others while you sleep. |

This sounds potentially dangerous, but it actually happens to everyone while they sleep. The National Sleep Foundation explains your throat muscles relax and become narrower during your slumber, and your tongue falls backwards as well. Here’s the thing, though: This narrowing can cause the walls of the throat to vibrate as you breathe in, inducing the ever-annoying sound of snoring. And the closer together those walls are, the louder the snore.

There are a few reasons why you may be more prone to snoring than others. For one, aging causes your throat muscles to relax gradually over time. And having enlarged tonsils or seasonal allergies can also cause the issue. Snoring may seem generally harmless, but it’s important to note about half of all people who do this also have sleep apnea.

5. You might have full-body jerks

woman who is trying to sleep

Some people have full-body jerks so severe they wake up in the middle of the night. | Thinkstock

The night is quiet, you’re relaxed, and you’re finally drifting off to sleep. But then, out of nowhere, your body decides to spasm back to life one final time before you rest. What gives? Well, Live Science says these hypnagogic jerks are actually quite common. Most people report having them as they’re falling asleep, but you actually may be having them multiple times at night and forgetting about them by morning.

Researchers aren’t totally sure why this phenomenon occurs, the story says, but they have their ideas. One is from an evolutionary standpoint: When humans were primates, they probably spent a lot of time in trees. Your muscles relax as you fall asleep, but your brain thinks you’re actually falling out of a tree, and thus jerks you back to wakefulness. Other scientists believe your nerves are simply misfiring as you’re preparing for slumber.

6. Your brain makes connections

Concept of dementia disease and a loss of brain function

Remember the names to all your new co-workers? Your brain was helping you do that while you slept. |

You might feel like sleep is the perfect opportunity for your brain to take a break from all the hard work it does during the day, but this organ is hard at work all through the night. The National Institutes of Health explains sleeping helps you remember new memories and link older memories to the newer ones you’ve made. In fact, getting a solid night’s rest is so crucial for your memory that researchers suggest your ability to learn new things drops by about 40% if you haven’t slept.

Studies performed in 2013 also suggest your brain might be hard at work cleaning house and removing toxins while you sleep. These studies were performed on mice, so we can’t say for sure whether it works the same way in humans. But the researchers suggest certain neurological disorders could be treated or prevented by looking more into how the brain clears itself.

7. Growth hormones are released

man exercising in the gym

If you want to build muscle, you definitely have to sleep. |

While you might be spending hours at the gym each day, you shouldn’t expect to see much progress if you’re not getting adequate sleep. The National Sleep Foundation explains your body releases growth hormones during the most restorative stage of sleep. For kids, this is essential for their development. But it’s also important for adults, as it aids in tissue growth and repair.

Make sure you’re getting a good night’s rest — you can really disrupt these hormones if your sleep patterns are off. And according to Tuck, the production of these growth hormones steadily declines as you age. And lower levels generally correlate with a higher risk of heart disease and diabetes.