I know you’re familiar with the term biological clock, but this doesn’t only apply to women wanting to have babies by a certain age.  It’s actually much more basic than that. Have you ever thought about why you go to sleep at night and wake in the day? Or how things like jet lag can have such a huge impact on your body?  Our circadian rhythm sleep and wake cycles are very important when it comes to the state of our health, and we often take them for granted.

So if you’re curious about how your biological clock works, what is circadian rhythm sleep and how it relates to our health keep reading.  And not to worry, because if you’re thrown off for some reason I’m also going to share some of my favorite tips for getting back on track.  

What are Circadian Rhythms

A circadian rhythm is just a fancy word for the biological, mental and emotional processes you move through in a day. When it comes down to a circadian rhythm definition there are a few things you should know: 

  • It’s based on a twenty four hour cycle. 
  • While they are happening inside the body, they can be affected by external factors like light, travel, and new habits.
  • They coincide with differences in temperature.  This is why your basal body temperature, immediately after waking, will be different than your temperature throughout the day.

Circadian rhythms have been studied in plants, animals, and even fungi but the circadian rhythm in humans is unique because we do things to interrupt our natural cycles while plants and animals don’t.  Factors that affect circadian rhythms are working night shifts, crossing multiple time zones at once like in long distance flights, caffeine, and using electronics or bright lights after dark 

All of these things can disrupt the sleep wake cycle, appetite, and mood because they throw off circadian rhythm hormones like melatonin. This is the hormone that makes you feel sleepy at night and is released by the hypothalamus in the brain. In a healthy person, melatonin is usually triggered by darkness. 

So how do circadian rhythms work exactly? Well that little part of the brain called the hypothalamus has a group of neurons inside of it that acts as a master clock for the body.  Depending on different external cues it will tell you when you’re hungry and tired, keeping the body on this 24 hour cycle that repeats each day.  

Natural Circadian Rhythms

Why are circadian rhythms important? If you want to think about a circadian rhythm chart, it might look like a clock. And when the clock works on roughly the same cycle each day, the body works like a well-oiled machine. It produces all the right hormones and chemicals at the right times that regulate blood pressure, appetite, metabolism, reproduction, sleeping, waking and even bowel movements. The brain and body are in sync and know in general what to expect. 

This could be different depending on your individual habits, but say around 6:30 am your body slows down melatonin production so you can wake up.  Around an hour later you’re more likely to have a bowel movement, and your appetite would increase for breakfast. This happens again around lunch and dinner and digestion works optimally.

Body temperature is lower in the morning and higher in the evening and blood pressure also fluctuates, raising throughout the day.  Your body might start to wind down around 9:00 pm, releasing melatonin to make you sleepy in preparation for bed. All of these changes throughout the day affect things like the endocrine system which regulates all your hormones from the thyroid glands to the reproductive system.  

It’s pretty complex but these are the basics of your circadian rhythm sleep and wake cycles, and when they are functioning optimally, your body’s metabolism fluctuates in a way that supports healthy digestion, you don’t suffer from any major fatigue, and you have the energy you need to move through the day. This is the basis for a healthy mind and body, but as we all know sometimes these get thrown off. So what happens then?

Disrupted Circadian Rhythms 

While the most common and well known circadian rhythm disorder is jet lag, there are a number of other problems that can occur in people of all ages.  Some of these are (1):

Non-24 Sleep Wake Disorder

This happens most often to people who are blind and their sleep cannot get regulated by light and dark. 

Shift Work Sleep Disorder

This occurs in people who work nights for a prolonged period of time and therefore their bodies can’t attune to regular sleeping and waking times. 

Delayed Sleep Phase Disorder

People who stay up very late and sleep in have this disorder since their sleep isn’t regulated by light and dark. 

You might know a few people in your life right now who have circadian rhythm disorders and don’t even realize it.  That’s because we have moved away from what’s natural to the point that we think it’s normal for someone to stay up until 2 am every night, when in reality it’s not!  This can have a profound effect on health, but before we go there, let’s talk about what lifestyle factors affect circadian rhythms.

Jet Lag

This happens when you travel across time zones and your mind and body clock conflicts with the signals you’re getting from the outside world.  So basically your body thinks it should be nighttime but you arrived in a place where it’s morning. 

This can cause insomnia, fatigue, appetite changes, constipation, irritability and even nausea or headaches. Pilots, flight attendants and other people who travel extensively for work are most affected and it can take days to adapt to a new time zone.

Screen Time 

So how do electronic screens affect circadian rhythms? As we know, our brains interpret light as a signal to wake up, so if you’re watching TV late into the night or looking at your phone, your body won’t be producing the melatonin it needs to fall asleep.  

The same is true if you wake up in the night and take time to scroll through your phone.  Blue light exposure is equivalent to the midday sun, so this digital light is very confusing to the brain and can totally disrupt your circadian rhythm sleep cycles. 

Shift Work

Shift work is incredibly damaging to the circadian rhythm sleep and wake cycle. This is especially true for doctors and nurses in hospitals who are exposed to fluorescent light while working nights because they are compounding night shifts with bright light very similar to electronics.  

Basically in any kind of shift work, you’re fighting sleep and telling your body not to produce melatonin at night when it gets dark.  And in order to stay awake when your body is tired you produce more adrenaline and stress hormones. Daytime sleep is never as good and it is difficult to get into a regular routine on days off, leading into other circadian rhythm disorders that cause you to stay awake late into the night and sleep in. While these things may not sound serious, disrupted circadian rhythm sleep can lead to other issues. 


As we know, even drinking caffeine too late in the day can throw off circadian rhythm sleep and wake cycles.  But the same goes for medication. Some blood pressure medicines make people stimulated and jittery, as do thyroid medications, anti-anxiety or antidepressants and prescriptions for ADD or ADHD.  Basically any medication you’re taking that lists “fatigue” or “restlessness” as side effects could disturb your circadian rhythms.  

You can try to work with your natural body clock by taking medications that cause fatigue later in the day, or the stimulating ones in the morning.  But this isn’t always possible, and is something to talk over with your doctor before making any changes. Best case scenario would be to avoid prescription meds, but I know that’s not always possible either. 


As we get older melatonin production can change and the body clock becomes slightly unregulated.  This is why often times people in old age get tired much earlier and wake earlier. The same goes for newborn babies.  In the womb babies aren’t on a circadian rhythm in sync with night and day, and need time after birth to adapt to this.

Pregnancy and Postpartum

Pregnancy hormones can change your circadian rhythms and so can postpartum. Besides all the hormonal changes, babies need to be fed at all hours of the night, causing disrupted sleep patterns. Sleep deprivation for any reason will alter the circadian rhythm sleep and wake cycles.  

This leads me to how abnormal circadian rhythms affect your mental health.  

How Abnormal Circadian Rhythms Affect Your Mental Health 

Seasonal Affective Disorder

This is a really common way to understand how light can affect your mood.  SAD is a disorder that occurs when people have normal mental health except during winter, when they suffer from mild to severe depression.  

Because it is linked to delayed circadian rhythm sleep, places like Alaska and Sweden which have prolonged and very dark winters tend to have more people suffering from SAD. Using bright light therapy can be helpful for treating it, especially if you start a protocol early enough, before Winter and depression set in.

Depression, Anxiety, and Difficulty Concentrating

Like seasonal affective disorder, people with disrupted circadian rhythm sleep cycles for any reason may experience bouts of depression or anxiety.  In fact, a study done in 2009 found that men who worked nights for over four years had more depression and anxiety than men who worked days (2).

One guaranteed symptom is a decrease in cognitive function, or the ability to concentrate and problem solve. Ask any new, sleep deprived, parent and they will agree with this one. 

But mental health isn’t the only thing that gets compromised from circadian rhythm sleep disruptions.  So how can abnormal circadian rhythms affect your physical health?

Sleep Disorders 

This one seems pretty common sense, but throwing off your circadian rhythms can have long lasting impacts on your sleep patterns.  People who work night shifts may suffer from  insomnia on their nights off and then extreme fatigue during the day.  Anyone who struggles with insomnia knows how hard it is when you’re exhausted all day long and then wide awake when it’s finally time to rest.  

Hormonal Changes

Remember how we talked about circadian rhythms being regulated by the master clock in the brain?  Well this little gland, the hypothalamus also affects our other hormones. I know when you think of hormones, you usually think about reproductive stuff, which is true.  Disrupted circadian rhythm sleep cycles can affect your fertility and menstrual cycles because melatonin (the hormone that’s released when you sleep) also keeps estrogen in check.

But then you’ve got other hormones that can be affected, like the thyroid hormones that impact metabolism, or cortisol and other stress hormones that get pumped out of your adrenal glands. These stress hormones can raise your blood pressure and heart rate, causing a lot of unnecessary physical stress. 

Weight Gain 

Remember that your metabolism is regulated by hormones, and disruptions in your circadian rhythm sleep cycles can interfere with your natural hormone production.  Besides this, getting too little sleep decreases your body’s leptin production, which is a key hormone for telling the brain, “there’s no need to eat, I’m full!” It also encourages the production of ghrelin which is the hunger hormone (3).  

So regardless of what you’re eating, if you are totally sleep deprived then your body might still be signaling a hunger that you can’t turn off!  This obviously leads to unnecessary weight gain and an unregulated appetite. 


You know the drill when you’re sick: rest and drink lots of  fluids. That’s because when you’re sleeping your body takes that time to clean up with a detox, allowing your immune system to do it’s work.  And drinking lots of fluids helps to flush toxins out of the body.

But science is now finding that we have a gene that could be controlling our immunity. The interesting thing about this particular gene is that it is connected to our circadian rhythms (4).  This means that if your circadian rhythm sleep cycles are disrupted, your immune system may not be functioning as well.  

So now that we’ve talked about all the things that can be affected by your circadian rhythms, what can you do to make sure they are working at their best?  

How to Get your Circadian Rhythms Healthy 

If you’re a person who has disrupted your natural circadian rhythm sleep and wake cycles and you want to get back on track there is a lot you can do to correct them, ranging from diet to sleep hygiene to changing out the lights in your home.  So keep reading because I’m going to share what you can do to get your circadian rhythms back into balance. 

Light Exposure

The number one thing you can do to re-establish healthy circadian rhythm sleep is to make sure when you go to bed at night, you keep your room in total darkness. That might mean black out curtains, especially if you live in a city or with a lot of street lights around you.  

The reverse goes for the daytime.  Expose yourself to as much bright, natural light as you can during the day so that your body can set its circadian rhythms.  Get outside in the sunshine on your lunch hour, or take short breaks and get a walk in. As the sun goes down in the evenings, keep the lights in your home low, or better yet use an incandescent bulb. 

And remember how the blue light from your phone is like midday sun? That’s right, leave the phone alone and just relax and wind down at night.  This will help your body produce the melatonin you need for sleep. If you absolutely must be on your phone or computer, try blue-light blocking glasses

But the more you get into the habit of relaxing without your phone at night in dim lighting, sleeping in total darkness, and getting out into the sunshine during the day, the quicker your circadian rhythm sleep cycles will become regulated. 


That’s right, there is actually a circadian rhythm diet.  And it’s less complicated than you think. Here are the basics:

Eat During the Day and Fast at Night

You’re probably familiar with intermittent fasting, which is similar to this style of eating.  But if you follow this rule it keeps your calories under control and works with your circadian rhythms and metabolism. Make sure to eat dinner as close to sunset as possible, but before sunset is even better. 

Eat Your Biggest Meal in the Morning

It’s pretty common for people to say that your body burns the most fat in the morning and “breakfast is the most important meal of the day.” But it’s true.  Give it a try, and eat your heaviest meal in the morning. You might find yourself having more energy, less cravings and bypassing that mid afternoon slump. Then eat your lightest meal for dinner. This way your body can detox at night without working so hard to digest heavy food. 


There are some basic lifestyle changes to make if you want to get your circadian rhythm sleep and wake cycles back in alignment.  But just like eating during the day and fasting at night, they are simple!  

Stick to a Bedtime!

Ideally you’d want to get in bed by ten and wake up around six, which would allow for eight hours of quality sleep and follows a healthy circadian clock.  I know this isn’t always realistic, but aim for sticking to this as much as possible.  And if 10-6 doesn’t work for you pick a bedtime that does. Maybe you have young kids and 9-5 works better, or 11-7.  But being in bed before midnight is important! 


Exercising at the right times of day helps keep your circadian rhythm sleep and wake cycles in check. Exercise releases cortisol and endorphins which can be too energizing late in the day.   A recent study found that exercise impacts thyroid stimulating hormone, melatonin and even blood pressure (5). 

But how does exercise help correct circadian rhythms?  I’ll keep it simple.  If you want help resetting your circadian rhythm sleep cycles make sure to get your exercise early in the morning around 7 am, or midday between 1pm-4pm.  This also works for people who go out on weekends and have a hard time getting back into their routine Monday morning.  So if that sounds familiar, get your exercise Sunday afternoon between 1-4.  

This is a pretty extensive guide on your circadian rhythms, what can go wrong when they’re off track and how you can fix them.  Your health can benefit just by following a basic routine for sleeping, eating and exercising.  It doesn’t have to be complicated, it just requires a bit of discipline. 

But now I’d love to hear from you.  Do you have anything interesting to share about how the circadian rhythm sleep and wake cycles work?  What about some helpful tips for getting back into balance when things feel off? Leave us a comment below! 



  1. WebMD (2019). “Sleep and Circadian Sleep Disorders.” Retrieved from: https://www.webmd.com/sleep-disorders/guide/circadian-rhythm-disorders-cause#1
  2. Lieber, Mark (2018). Maintaining a A daily Rhythm is Important for Mental Health, Study Suggests.” Retrieved from: https://www.cnn.com/2018/05/15/health/circadian-rhythm-mood-disorder-study/index.html
  3. Mercola (2011). “The Sleeping Habit that Can Make You Hungrier, Plumper, and Forgetful.” Retrieved from: https://articles.mercola.com/sites/articles/archive/2011/03/16/this-modern-day-convenience-can-disrupt-your-metabolism-and-interfere-with-learning.aspx
  4. Pearson, Catherine (2012). “Circadian Rhythms Influence Immunity, Study Says.” Retrieved from: https://www.huffpost.com/entry/circadian-rhythms-immunity-immune-system_n_1281654
  5. Holmer, Brady (2019). “Body Clock: Timing Exercise for Sleep and Circadian Health.” Retrieved from: https://medium.com/@bradyholmer/body-clock-timing-exercise-for-sleep-and-circadian-health-17266eb62ad3

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.