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Here’s What Happens to Your Body When You’re Asleep

By Elisa - Jenny Craig


Raise your hand if you feel like there aren’t enough hours in the day to get everything done (we get it!). But if you’ve been spending more time counting items on your to-do list than counting sheep, it may be worth taking a look at your sleep habits. While staying up late to finalize a work project or catch up on your favorite shows might seem harmless, consistently skimping on sleep can have a bigger impact on your health than you might think.

Fast facts on sleep

  • 42% of adults get less than seven hours of sleep each night, according to a 2014 report1 — which is less than the seven to nine hours recommended by the National Sleep Foundation.2
  • Only 10% of Americans prioritize sleep over other everyday activities, including their hobbies, work and their social lives, according to a 2018 poll conducted by The National Sleep Foundation.3
  • Although 65% of Americans think getting enough sleep makes them more effective people, only 41% consider how much sleep they need to prepare for the next day.3


Sleep-Cycles-amanda-jones-1117789-unsplash.jpgSo why do those seven to nine hours a night matter when it comes to your health? It all starts with the different stages of sleep your body experiences when you’re at rest. Read on to find out what really happens to your body once you fall asleep and how you can start prioritizing your z’s for better health.  

What happens to your body during the stages of sleep?

Scientists once thought that during sleep, the body would shut down and enter a state of recovery.4 However, with advancements in technology, researchers now have a better understanding of what happens when your body is at rest. Not only are there two different types of sleep: Rapid eye movement (REM), and non-REM (NREM) sleep — but your body typically goes through five different stages of sleep throughout the night:5


  • Stage 1 - (NREM sleep). You’ll experience this stage within minutes, and in some cases, seconds after falling asleep. Since this stage of sleep is very light, you can easily wake and may even experience muscle twitches as you start to drift off — if you’ve ever taken a “catnap,” you’ve entered this stage.4-5



What happens: your eye movement begins to slow down and your muscles start to relax.  


  • Stage 2 - (NREM sleep). You’ll likely spend more time in this stage of sleep than in any other stage.5 You’ll still be sleeping lightly, but this stage sets you up for deep sleep.



What happens: Your heartbeat, brain wave activity and breathing slow down, your muscles relax even more, and your eye movement stops.


  • Stages 3 and 4 - (NREM sleep). During these stages of sleep, you’re experiencing deep sleep. If something disrupts you, it will probably feel hard to wake up.



What happens: Your muscle activity stops — this is when your body starts repairing muscles and tissues, stimulating growth and development and increasing immune function.4 Heartbeat and breathing slow even more.5


  • REM sleep. It takes about 90 minutes to enter the REM stage after you’ve fallen asleep.4 As its name suggests, your eyes will move quickly and in many directions during this cycle.4 It can last up to an hour, with most adults experiencing five to six REM cycles every night.4  



What happens: Most dreaming happens during REM sleep, and it’s also the time when your brain processes and stores information from the day before into your long-term memory.4


Each stage of sleep is important to your body — but if you aren’t sleeping enough or are not reaching the restorative deep sleep state, it could have an impact on your health.

How sleep patterns are controlled

Sleep-Cylces-Disconnect-charlz-gutierrez-de-pineres-64078-unsplash.jpgAlthough the amount of sleep each person needs often varies, the National Sleep Foundation recommends that most adults need between 7-9 hours.2 Your sleep patterns are regulated by your circadian rhythms, natural cycles that occur every day.6


Your circadian rhythms contribute to many different functions including wakefulness, your eating habits,6 and may even impact your weight loss efforts. These rhythms also control your sleep timing, causing you to feel awake in the morning and tired during the evening hours. Light is the most important cue for your circadian rhythms, and getting too much or too little could disrupt them.6 Irregular rhythms have been linked to various health conditions, including depression, obesity and diabetes.6


Practicing good sleep hygiene, such as going to sleep and waking up at consistent times, helps support these cycles. Reducing your exposure to blue light in the evenings, including looking at your phone and watching TV right before bed, may also support better sleep.7

The benefits of getting great sleep

By following your natural sleep patterns and getting sufficient sleep, your health may benefit in several ways:


You may be able to better manage your appetite. A recent study found that women who had insufficient sleep for just one night had higher levels of ghrelin in their body the next day, a hormone that signals hunger.8 The women reported increased hunger and food cravings and also selected larger portions of food, especially at lunch, the following day. While more research is still needed, this study supports other findings that suggest getting adequate sleep may help to regulate your hormone levels, and consequently, your appetite.8


You may be less likely to get sick. Getting eight hours of sleep or more may help your immune system fight off the common cold. One study reported those who slept for seven hours or less were more likely to get sick, compared to those who slept more.9


You may lower your risk for high blood pressure and heart disease. Too little sleep may put your heart health at risk. Researchers are making more connections between sleep deprivation, heart disease and high blood pressure. In one study, middle-aged people who slept for five hours or less had a significantly increased risk of high blood pressure.10 In a separate study, men who slept less than five hours at night doubled their risk of having a heart attack or stroke – similar to the effects of having diabetes or being a smoker.11


Sleep-Cycles-Weight-Loss.jpgYou weight loss efforts may benefit. Getting quality sleep can help support your weight loss efforts. By eating during the first 12 hours of the day and refraining from food or caloric beverages for the remaining 12 hours (which includes sleep), you’ll work with your circadian rhythm and your body’s natural processes. Since your metabolism is most efficient during the day, fueling your body during daylight hours and avoiding late-night meals and snacks (and making sure to get adequate sleep) can help to optimize weight loss. Jenny Craig’s Rapid Results program leverages the Nobel-Prize winning science of circadian rhythms.


Even if it’s only a small change at first, making a commitment to change your sleep patterns may benefit your health. Not sure where to get started? Follow these tips to help get a better night’s sleep.


Want more on the latest in health and wellness? Download our free Healthy Edition e-magazine today!





[1] https://news.gallup.com/poll/181583/getting-sleep-linked-higher.aspx

[2] https://www.sleepfoundation.org/press-release/national-sleep-foundation-recommends-new-sleep-times

[3] https://www.sleepfoundation.org/media-center/press-release/2018-sleep-in-america-poll-shows

[4] https://www.sleep.org/articles/what-happens-during-sleep/

[5] https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep#2

[6] https://www.nigms.nih.gov/education/pages/Factsheet_CircadianRhythms.aspx

[7] https://www.scientificamerican.com/article/apple-s-night-shift-mode-how-smartphones-disrupt-sleep/

[8] https://www.mdpi.com/2072-6643/11/3/663/htm

[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2629403/

[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845795/

[11] https://www.businessinsider.com/sleep-deprivation-increases-heart-disease-risk-2018-8

Elisa Hoffman

bio-photo-Elisa.jpg.ea6b8a205d9e2f742b035cb498a3b0bb.jpgElisa is a content marketing manager for Jenny Craig with over ten years of experience working in the health and fitness industry. She loves sharing her passion for living a balanced and healthy lifestyle. A San Diego native and an endurance sports enthusiast, you can usually find her swimming, biking along the coast highway or running by the beach in her free time. Elisa holds a Bachelor of Arts degree from California State University Chico.


Favorite healthy snack: mozzarella string cheese with a Pink Lady apple.







This article is based on scientific research and/or other scientific articles and is written by experienced health and lifestyle contributors and reviewed by certified professionals.


Our goal at Jenny Craig is to provide the most up-to-date and objective information on health-related topics, so our readers can make informed decisions based on factual content. All articles undergo an extensive review process, and depending on the topic, are reviewed by a Registered Dietitian Nutritionist (RDN) or Nutritionist, to ensure accuracy.


This article contains trusted sources including scientific, peer-reviewed papers. All references are hyperlinked at the end of the article to take readers directly to the source.




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