There is more to your circadian rhythm than determining when you are awake and when you sleep. Your circadian rhythm plays an important role in regulating all functions of your body. And it optimizes these too. Every single day. At least if you let it do so.
Why is the circadian rhythm so important for you? Your circadian rhythm optimizes the timing of every biological function of your body. This is important because your body cannot do everything at the same time. Your circadian rhythm regulates your physiology, your cognitive functions, and all your major systems – including sleep and wakefulness.
Read on to get a full understanding of:
- What your circadian rhythm regulates for you
- What it means for you to live aligned with your circadian rhythm
- What it means to live against your circadian rhythm
- Two hacks that allow you to align with your circadian rhythm
- My personal experiences and your key takeaways
One thing I can tell you already now: Your circadian rhythm has a bigger impact on you than you might imagine. On every single part of your life. But let’s not get ahead of us.
Your Circadian Rhythm
What Your Circadian Rhythm Regulates for You
Just picture yourself as your body for a moment. You are in charge of everything. What would you want to spend your time on?
- Well, you have to ensure that you get in enough food so that you have enough energy.
- You want to use your energy wisely. That means to use it in the moment if you need to. For example, for maintaining your daily functioning. And to store the rest for later. Ok, you might not want to store additional energy if you had the choice. But that helped our species survive, so we have to deal with it now.
- You want to grow. You want to get taller over your early years. And you might want to build muscle mass later on.
- You want to protect yourself against anything harmful. This could be anything that would make you sick. Or that would want to eat you.
- You want to repair yourself. Especially if you weren’t able to fully protect yourself.
- And, last but not least, you also want to reproduce.
From the perspective of your body, this is what you would want to spend time on. And this is also what every other living organism spends its time on.
Now to the second part of this. What would it mean for you to spend your time on any and all of these things? Could you do everything at once? Or would it be better to have specific times for specific functions?
You are right, you can’t do everything at once. This is where your circadian rhythm comes into place. But don’t just take my word for it. Take it from Satchin Panda, one of the world’s leading chronobiologists (those who study circadian rhythms):1
“Circadian rhythms optimize biological functions. Every function in the body has a specific time because the body cannot accomplish all it needs to do at once.”Satchin Panda
The timing of everything that your body needs to accomplish is optimized. Over a daily cycle of twenty-four hours. Thanks to your circadian rhythm.
In general, there are three functional categories that your circadian rhythm regulates for you:2
- Your physiology
- Your cognitive functions
- Your major systems, such as your blood and immune systems, your vascular systems, and your metabolism
And how does this optimization look for you on a daily basis? Let’s have a look at a few examples. Those will also give you some more detail on why a strong circadian rhythm is so important for you:
- First and foremost, your circadian rhythm determines when you want to sleep and when you want to be awake.3
- Your body produces hormones at different times. Your “stress” hormone cortisol – that helps you wake up and get ready for the day – is naturally high in the morning.4 Your “sleep” hormone melatonin is naturally high in the evening.5 As long as you have a strong circadian rhythm.
- Your core body temperature changes over the course of day and night. It is coldest at night and warmest in the late afternoon/ early evening.6
- In the late afternoon/ early evening (at the peak of your body temperature) you also reach the peak of your physical performance. Levels of coordination, strength, and perceived exhaustion all align in your favor.7
- Your ability to concentrate fluctuates over the day. You are better at logical thinking at some times of the day than you are at creative thinking. And the other way round.8
- Also, your pain perception varies during the day. Got a painful event coming up? Better schedule it for when your perception of pain is going to be lowest.9
- And many types of medication are most effective during a specific time of day. This is because they target a specific part of your body. And each specific part is optimized in its timing.10
Ok, you have seen the big picture of what your circadian rhythm regulates and optimized over your day. Over every single one of your days.
In the next part, I want you to fully grasp the importance of having a strong circadian rhythm. For this, I’ll walk you through how a day could look like for you if you live aligned with your circadian rhythm. And then we’ll have a look at what it means if you live against your circadian rhythm.
Living in Alignment
What Does It Mean to Live Aligned with Your Circadian Rhythm
Let’s get more concrete here and have a look at what it means for you to be aligned with your circadian rhythm. And the implications for your day-to-day life:1,11
Before you wake up: Your circadian rhythm reduces the production of your sleep hormone melatonin. Your breathing and your heartbeat become slightly faster. And your blood pressure and core body temperature rise slightly.
When you wake up: When you live aligned with your circadian rhythm, you can wake up without an alarm clock. You feel rested, full of energy, and ready to start the day. If you wake up with an alarm clock, your body has to stop its nightly tasks. It has to shift focus and start the ones that get you ready for your day.
After opening your eyes: You should receive plenty of sunlight. Or at the least very bright light. Your eyes can then signal your brain that sleep is over and the day starts. Your body will stop producing melatonin (your sleep hormones) and start producing cortisol. You may know cortisol as the “stress hormone” to avoid. But in the morning it is vital for you. It helps you feel more alert and energized.
In the first half of your day: This is the time when your brain normally is at its peak. Get your most productive work done. Especially everything that needs logical and abstract thinking. Don’t waste this time with mundane tasks or on social media.
During your afternoon: You are likely to see a dip in your mood, in your ability to concentrate, and in your general performance here. This is normal. But you can refresh yourself by taking short breaks. Especially outside, where your eyes receive plenty of natural light. Another great way is to get a quick session of meditation in (I use the headspace app every day and I love it). Or you can even have a short nap of ideally ten to twenty minutes.
In your late afternoon to early evening: This is the time when your core body temperature is at its peak. And the time when your physical performance is at its peak too. Also, your muscle tone peaks and coordinative functions increase. This makes you less prone to injuries and to perceive your exercise intensity to be at a lower level.
Also in your late afternoon to early evening: After you consumed your last calories, your digestive process still goes on for about two to three hours. Only then can your body prepare to wind down, to cleanse, and to rejuvenate you.
During your evening: Your body starts producing your sleep hormone melatonin (if you don’t interrupt it with bright lights or screens). This helps you to relax and to prepare you to sleep. Your core temperature also starts to drop.
When you go to bed: When you are aligned with your circadian rhythm, your core temperature will be at its lowest. And you will be able to fall into a deep sleep without too much effort.
Here you have seen the benefits of living your days aligned with your circadian rhythm. But what about the consequences of living against your circadian rhythm?
Consequences of Misalignment
What Does It Mean to Live Against Your Circadian Rhythm
Living against your circadian rhythm can influence all aspects of your health. And those consequences can last longer than a single day. Much longer.
It is easy for you to see if you are aligned with your circadian rhythm. You can simply double-check the list of benefits from the last section. If you fall short on several of these, chances are that you are living against it. And if you live against your circadian rhythm, you will not be able to reap all its benefits. Sounds simple, right? Sadly, the majority of us live against their circadian rhythm – at least during their working days.2,12
Find out all about this phenomenon in this post about “What Is Social Jet Lag and How to Overcome It.”
But there’s more than that. Much more. The major problems of living against your circadian rhythm take longer than one single day. Let’s be brave and have a look at these now, shall we?
Below are some of the health implications for you if you live against your circadian rhythm:1
- This is what happens if you disrupt your circadian rhythm for one or a few days: Your brain cannot ensure that your body is doing the right things at the right time. Neither your body nor your mind will function optimally. Remember, your body cannot fully accomplish any process that you interrupt.
- This is what happens if you disrupt your circadian rhythm for weeks or months: The most severe problem? Your immune system. It cannot work anymore as it should. This makes you more prone to infections and communicable diseases.
- This is what happens if you live your life against your circadian rhythm: You are now also more prone to non-communicable diseases. Those that you develop because of your lifestyle. Also, those that are chronic and normally come to you to stay with you. And also those that account for 71% of all deaths globally.13
Ok, that was a high-level overview to already give you a glimpse into the issues that you can run into. At least if you live against your circadian rhythm. I know that those lines might already have been tough to read for you. Be strong now with the overview of what that concretely means for you.
One of the leading chronobiologists, Till Roenneberg, summarized the consequences of living against your circadian rhythm into the following three categories:14
|Cognitive Responses||Emotional Responses||Somatic Responses|
|Reduction in concentration||Exhaustion||Drowsiness|
|Reduction in performance||Increases irritability||Microsleeps|
|Reduction in attention||Mood fluctuations||Unintended sleep|
|Reduction in memory||Anxiety||Sensations of pain|
|Reduction in recall of events||Depression mood||Sensations of cold|
|Reduction in multitasking||Frustration||Cardiovascular disease|
|Reduction in decision making||Anger||Risk of cancer|
|Reduction in creativity||Increased impulsivity||Metabolic abnormalities|
|Reduction in productivity||Decreased motor skills||Weight gain|
|Reduction in socialization||Increased stimulant use||Risk of Diabetes Type II|
|Reduction in communication||Increased sedative use||Reduced immunity|
|Alcohol use/ misuse||Disorders of the HPA|
Wow, that’s quite a list to avoid, right?! But I hope that now that you know, you can also take the first steps in the right direction. One step at a time. And here are two steps that I would recommend you right now:
- Find out all you need to know in this post about “How Does Your Circadian Rhythm Work“
- Find out your next steps in this post about “How to Get Your Circadian Rhythm Back on Track“
Let’s have a look at a quick overview of how you can live more aligned with your circadian rhythm next. And then I’ll share a few of the things that have helped me.
How Light and Time-Restricted Eating Helps You to Align With Your Circadian Rhythm
Now that you know whether you live rather aligned with or rather against your circadian rhythm, what next? Let’s get you closer toward living in alignment!
Those are the two factors that will have the biggest impact on you. And you can mostly control both of them: First, light exposure. Second, time-restricted eating. Let me explain.
Light exposure: Your circadian rhythm is centrally governed by a small part of your brain (called the SCN) that is directly connected to your eyes. This SCN sets your internal time. Your internal time controls your circadian rhythm. And all of these steps are based on your light exposure.
What does that practically mean for you? Get as much natural sunlight during the day as possible! This will set your circadian rhythm up for your day. Indoor light intensities don’t even come close to that. And cut back on any screens and also LEDs during evening and night. This would prevent your circadian rhythm from preparing you for the night.
Time-restricted eating: The circadian rhythm of your internal organs are influenced by your liver. And your liver is influenced by the timing of your food intake. You should be eating when your body is optimally prepared to digest food. And stop eating early enough so that your stomach doesn’t interfere with your nightly preparations.
What does that practically mean for you? Practice time-restricted eating. Allow your circadian rhythm to focus on functions other than digestion. You mustn’t eat too late in the evening. And for your stomach, all calories count. No matter if it is a full meal or a little snack or a caloric drink. It will have to go through its full digestion process. Try to stop eating in the early evening or even late afternoon and discover how it will improve your sleep quality.
My Personal Experiences
How does it sound to you being aligned with your circadian rhythm? To me, it sounds pretty awesome! And this is also why I have made it a daily goal for many years now. Here is what has helped me:
- I wake up in the morning without an alarm clock.
- I get plenty of natural light, especially during the first half of the day.
- I shift my most important tasks to the morning.
- I shift my most intense sport sessions to the late afternoon/ early evening.
- I eat my last meal in the afternoon.
- I cut down screen time in the evening.
The most difficult part for you to implement would most likely be to wake up without an alarm clock. And that is normal. Nearly everybody uses an alarm clock.15 But what I can tell you is that light plays a key role to help you out here. Increasing natural light exposure in the first part of the day and cutting down on screen time in the evening will help you to achieve this too. So that you can get a headstart over nearly everybody. Give it a try!
Finally, there are four key takeaways that I want to share with you:
- Your body has to accomplish many functions during the day but can’t do them all at once. Your circadian rhythm optimizes your daily functions if you allow it to do so.
- You feel best when you align your daily rhythm with your circadian rhythm. This impacts your daily energy levels, your cognitive and physical performance, your health. And everything else.
- You limit your potential in all areas of your life if you live a life against your circadian rhythm. And you make your body more prone to a range of health issues, including chronic diseases.
- The most important factors to align with your circadian rhythm are your light exposure and your meal timings.
- You want to get as much natural light during the day and as little artificial light during the evening and night.
- And you want to stop eating early enough so that your body can prepare you to fall asleep. This allows your body to cleanse and rejuvenate you during your sleep and also improves your sleep quality.
And now back to you: If you reflect on your typical day, do you already live aligned with your circadian rhythm? If yes, what has helped you on that journey? If no, what would you change?
PS: If you found this information useful, spread the word and help those who would benefit most from it 🙂
- 1.Panda S. The Circadian Code. Rodale Books; 2018.
- 2.Roenneberg T. Internal Time. Harvard University Press; 2012.
- 3.Dijk D-J, Czeisler CA. Paradoxical timing of the circadian rhythm of sleep propensity serves to consolidate sleep and wakefulness in humans. Neuroscience Letters. January 1994:63-68. doi:10.1016/0304-3940(94)90841-9
- 4.Rohatagi S, Bye A, Mackie AE, Derendorf H. Mathematical modeling of cortisol circadian rhythm and cortisol suppression. European Journal of Pharmaceutical Sciences. November 1996:341-350. doi:10.1016/s0928-0987(96)00174-1
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- 9.Junker U, Wirz S. Review Article: Chronobiology: influence of circadian rhythms on the therapy of severe pain. J Oncol Pharm Pract. June 2009:81-87. doi:10.1177/1078155209337665
- 10.Smolensky MH, Hermida RC, Ayala DE, Tiseo R, Portaluppi F. Administration–time-dependent effects of blood pressure-lowering medications: basis for the chronotherapy of hypertension. Blood Pressure Monitoring. August 2010:173-180. doi:10.1097/mbp.0b013e32833c7308
- 11.Pink DH. When: The Scientific Secrets of Perfect Timing. Riverhead Books; 2018.
- 12.Jankowski KS. Social jet lag: Sleep-corrected formula. Chronobiology International. March 2017:531-535. doi:10.1080/07420528.2017.1299162
- 13.World Health Organization -. Noncommunicable diseases (NCDs), also known as chronic diseases, kill 40 million people each year. Non communicable diseases. https://www.who.int/news-room/fact-sheets/detail/noncommunicable-diseases. Published 2018.
- 14.Merrow M, Roenneberg T. Circadian clocks: how rhythms structure life. Presented at the: coursera; 2019; Ludwig-Maximilians-Universität München (LMU).
- 15.Pilz LK, Keller LK, Lenssen D, Roenneberg T. Time to rethink sleep quality: PSQI scores reflect sleep quality on workdays. Sleep. February 2018. doi:10.1093/sleep/zsy029