Your circadian rhythm goes beyond your sleep-wake cycle and influences virtually all aspects of your life and wellbeing. Yet, if you are like most people, then you don’t live aligned with it. Let me highlight the four main problems that prevent you from living aligned with your circadian rhythm. And then show you how you can overcome these to get your circadian rhythm back on track. This is also what some call to reset your circadian rhythm

How to get your circadian rhythm back on track? You can get your circadian rhythm back on track by aligning your light exposure and your eating timings. Get as much (natural) light during the day as possible and reduce (artificial) light exposure at night. Stop eating three hours before you go to bed and eat for fewer total hours during the day.

Read on to get a full understanding of:

• Why you need to increase your light exposure in the first part of the day & how you can do it
• Why you need to reduce your (blue) light exposure in the second part of the day & how you can do it
• Why you need to limit the total hours your organs need to work on processing food & how you can do it
• How you can use your exercise timing to your advantage
• How you can measure whether you are on track
• My experiences and your key takeaways

To get a detailed overview of why you need to get your circadian rhythm back on track, I recommend you start with the upcoming first part. This will also guide you to find out which of the practical tips will have the biggest impact on your specific situation.

If you directly want to jump to how you can get your circadian rhythm back on track, you can use the following for direct navigation to those practical tips most relevant to you.

Problem 1: You don’t get enough light during the day

Tip #1 Spend at least two hours outdoors during the first half of every day
Tip #2 Stay as close to windows as possible if you are indoors
Tip #3 Take artificial light showers during the day if needed
Tip #4 Don’t wear sunglasses (if you don’t spend the whole day outside)
Tip #5 Spend a weekend in nature

Problem 2 & 3: You get too much light & blue light during the evening and night

Tip #6 Adapt your home lighting for the second part of the day
Tip #7 Reduce blue-light emissions from your screens
Tip #8 Use blue-light filtering glasses
Tip #9 Avoid any (blue) lights at night

Problem 4: You eat for too long and/ or too late

Tip #10 Stop eating early enough in the evening
Tip #11 Eat for fewer hours every day

“Bonus Problem”: You don’t exercise at the right times

Tip #12 Use exercise to help align your circadian rhythm

Why to Get It Back on Track

Why You Need to Get Your Circadian Rhythm Back on Track

Your circadian rhythm was evolution’s way to align all functions in your body with the external day. To be more precise, to regulate your functions at the right time and in the right intensity based on the external time your body perceives. And your body perceives this external time through the light it receives.

Let me quickly summarize the most important parts of your circadian rhythm:

1. Your circadian rhythm is the natural, internal rhythm your body goes through every single day. It controls and optimizes all your functions and allocates a specific time frame to each. Your circadian rhythm is not exactly 24-hours long and comes from the Latin “circa” (about) and “dies” (day). (Read all about it in this post about “What Is the Circadian Rhythm and Why Do We Have One“)
2. 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 all about it in this post about “Why Is the Circadian Rhythm so Important for You“)
3. Your circadian rhythm is centrally controlled by a part of your brain called the SCN. The SCN gets your time of day information through light receptors in your eyes that are especially sensitive to blue light. Through this light information, it adjusts your circadian rhythm to your external day. (Read all about it in this post about “How Does Your Circadian Rhythm Work“)

Now, let’s start with the most important factor that influences your circadian rhythm: light.

Light is the biggest factor that influences your circadian rhythm. Through the right light intensity at the right time, your brain can set you up with a strong circadian rhythm. But with too weak a light intensity or light at the wrong time, your circadian rhythm gets off track.

And here is the biggest reason why you have to get your circadian rhythm back on track: the light information your brain receives to set your circadian rhythm doesn’t match what it needs. Let me explain.

The light information your brain expects is based on sunlight. All-day-long exposure to sunlight. 

And sunlight has two special properties:

1. The light intensity is crazy intensive during the day and nearly zero at night
2. The blue-light spectrum is strong during the day but not anymore during the evening and not at all during the night

These are also the two main ways we mess up our circadian rhythms. So let’s have a closer look at each of them next.

Light Intensities

Why You Need to Get Your Light Intensity Back on Track

The first problem is that you most likely don’t receive high enough light intensities during the day.

Up until before the industrialization, we used to work outside during the day. But then we more and more shifted our time spent into buildings. And light intensities outside are up to 1,000 times higher than in buildings.

Light intensity is measured in Lux. And natural sunlight intensity outside is about 10,000 Lux on overcast days and can reach over 150,000 Lux on the sunniest days. Do you want to take a guess what light intensities your brain needs to set you up for a strong circadian rhythm? Yes, anything roughly in this range.

Now, how much are light intensities inside a building? Well, that depends on how strongly lit it is. And how close to the window you are. But normally it is in the range of only a few hundred Lux.

How does that look like over a typical day? Let’s have a look at a concrete (yet still unpublished) study^​1​ about the difference in light profiles between somebody who works outside and somebody who works inside an office. To smoothen out the graphs and make them more meaningful, the light profiles are shown as a rolling two-hour average.

• 

• 

The first thing you might notice is the difference in the maximum two-hour Lux intensity of 110,000 vs 6,000. But even more dramatically, did you also notice the small blue graph below the green graph on the left side? And how relatively small this one is? Well, that’s the same graph from our average office worker on the right side. Just set to scale to our average outside worker. That’s quite a difference, right?

Now imagine that you are in charge of setting your circadian rhythm. And to get all your functions started and going at the right times, you expect outside light intensities of several thousands of Lux. Just like in the green graph on the left. But what do you receive? Mostly only a few hundred Lux. So what would you do? Maybe, just like your internal clock (remember, your SCN), you decide that this is not enough to set yourself up for a strong circadian rhythm.

Your internal clock most likely doesn’t receive high enough light intensities. The result? Your circadian rhythm (that follows your internal clock) cannot fully prepare you for the day. And that makes your circadian rhythm weaker. It is not able to optimize your functions for the day.

The second problem is that you most likely do receive too much light intensity during the evening and night.

You’ve seen the immense sunlight intensities during the day. And how we often fail to reach those when being indoors, where normally just receive a few hundred Lux. But what about the light intensities at night?

For a moment, picture a clear and bright sky, with a full moon and all the stars shining. How many Lux do you think you would receive from this night sky? Well, it’s actually much less than you might have expected. It’s less than one Lux. Yes, not even one single Lux.

Now compare that again with the hundreds of Lux you normally receive indoors, also long after the sun has set. Like that, these few hundred Lux don’t seem that insignificant anymore, right?

From a perspective of your inner clock, the presence of any light means that it can’t be night yet. And even a few hundred Lux are sufficient to tell your internal clock that it’s not night yet. Regardless of whether it is actually night or not. 

The result? Your circadian rhythm (that follows your internal clock) cannot prepare you for the night yet. And that makes your circadian rhythm weaker. It is not able to optimize your functions for the night.

Blue-Light Exposure

Why You Need to Get Your Blue-Light Exposure Back on Track

The third problem is that the light you receive during the evening and night is most likely too high in the blue-light spectrum.

Before I tell you more about why you are especially sensitive to blue lights, I want you to have a look at this beautiful picture of the midnight sun. Can you see the difference in light color that sunlight has over the course of a day (and night here)?

Now, if you could choose which light-color your eyes should be most sensitive to figure out when the day starts, which would you choose? Yes! The blue-light colors! And that is exactly what happened during evolution.

You actually have special light receptors in your retina, whose only job it is to tell your brain the time of day.^​2​ They do this based on the light information they receive. And they are especially sensitive to blue lights. (Read the full story in this post about “How Does Your Circadian Rhythm Work“)

Thanks to electricity you can stay awake long after the sun has set. But this is not the worst part yet. The worst part is that the screens of all of your devices, like your smartphone, your TV or your eReader, and also modern LEDs emit a lot of blue light. And you are most sensitive to blue light. 

Here is how blue light has an impact on the perceived light intensities during the day and night:

• During the day, your internal clock expects a lot of light and also a lot of blue light. Your screens and LEDs normally can’t match these intensities.
• During the evening and night, your internal clock expects hardly any light and no blue light. Your screens and LEDs easily go beyond those intensities.

The result? Your artificial blue lights are not strong enough to set your circadian rhythm (that follows your internal clock) up for the day. But they are strong enough to make your circadian rhythm weaker at night. Your circadian rhythm cannot prepare you for the night yet. It is not able to optimize your functions for the night.

Eating Timings

Why You Need to Get Your Eating Timings Back on Track

Light influences your internal clock (the SCN in your brain). And your internal clock is responsible to centrally set your circadian rhythm. Food, however, sets the internal clock of your organs. It sets their circadian rhythm

The first calories of the day tell the clocks in your organs like gut, stomach, or liver, to start their day. And your organs still need about two to three hours after to process any last calories you consumed, before they can stop their day. And change from digestion to repair and rejuvenation mode.

The fourth problem is that you most likely eat for too long and/ or too late, not giving your organs enough time to repair and rejuvenate.

Just think about a normal day of eating and drinking. When do you normally start with your first calories? Yes, also the calories in your coffee creamer count! And when do you normally stop with your last calories? Again, any calories in a snack or in drinks like wine or beer count!

If you are like most people, then:^​3​

1. You believe that you consume your calories in a twelve-hour window (and are not counting any drinks or late-night snacks).
2. You actually consume calories for fifteen hours or more.
3. You consume your last calories too late.

This leads to two big problems for you. First, your organs spend too much time with the digestive process and not enough in a repair and rejuvenate mode. Second, you further cut the repair and rejuvenate process of your organs short at night. This happens when you consume calories too late. Your organs then have to digest these. But that takes time. And your organs still have to continue with their digestive processes even if you go to sleep already. They just can’t do it as fast or effective anymore. 

The result? You don’t allow your organs enough time for their repair and rejuvenation mode. And you force them to continue their digestive processes at a time when it would be most beneficial for them to… Yes, to repair and rejuvenate. So you don’t allow your organs to follow their optimal circadian rhythm. And they won’t be able to optimize the timings of their functions. (Read the full story in this post about “When Is the Best Time to Eat – Based on Your Circadian Rhythm“)

Misalignment

Why You Do Not Want to Live Against Your Circadian Rhythm

Before we jump straight into the specifics of how you can get your circadian rhythm back on track, I would like to show you a summary of why you want to do so starting today. And why you may want to help your friends and family to do so too.

Below is a summary of what happens if you live against your circadian rhythm by the leading chronobiologist, Till Roenneberg^​1​. It is a summary of why you want to get your circadian rhythm back on track. Panda categorized the consequences of living against your circadian rhythm into three categories:

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

Get the full picture in this post about “Why Is the Circadian Rhythm so Important for You”

How to Get It Back on Track

How to Get Your Circadian Rhythm Back on Track

I do hope that the first part helped you understand why you need to get your circadian rhythm back on track. And that it also helped you to form your first ideas about your biggest opportunities for improvement.

Especially that second part is important for your first steps. Your biggest opportunities for improving your circadian rhythm will also have the biggest impact on you. Sounds logical, right? 

To help you find the right way to get your circadian rhythm back on track, I have divided the practical tips into our four problem categories from the first part above. Plus, I added a bonus category about exercise, which also helps you get your circadian rhythm back on track, however, in a less direct way than the others.

Problem 1: You don’t get enough light during the day

Tip #1 Spend at least two hours outdoors during the first half of every day
Tip #2 Stay as close to windows as possible if you are indoors
Tip #3 Take artificial light showers during the day if needed
Tip #4 Don’t wear sunglasses (if you don’t spend the whole day outside)
Tip #5 Spend a weekend in nature

Problem 2 & 3: You get too much light & blue light during the evening and night

Tip #6 Adapt your home lighting for the second part of the day
Tip #7 Reduce blue-light emissions from your screens
Tip #8 Use blue-light filtering glasses
Tip #9 Avoid any (blue) lights at night

Problem 4: You eat for too long and/ or too late

Tip #10 Stop eating early enough in the evening
Tip #11 Eat for fewer hours every day

“Bonus Problem”: You don’t exercise at the right times

Tip #12 Use exercise to help align your circadian rhythm

Side-note: With these tips, I have focused on the factors that most directly influence your circadian rhythm and that you can also control enough to make a difference. I left out other factors that either have a more indirect impact like caffeine (hint: stop around lunchtime so that it doesn’t interfere with your ability to fall asleep). Or factors that are out of your control like your social schedule, especially if you are a shift worker (in this case, still try to implement as many of the tips as possible).

Making small but specific lifestyle changes is the secret to getting your circadian rhythm back on track. So let’s dive directly into it.

Maximize Natural Light Exposure

#1 Spend at Least Two Hours Outdoors During the First Half of Every Day

A high light intensity triggers your internal clock. Especially if it is rich in blue-light rays. Sunlight during the first half of the day – surprise – fulfills both of these criteria.

Or better the other way round, because sunlight in the first half of the day both has a high light intensity and is rich in blue-light rays, we developed our receptors (called melanopsin) that want both of these qualities. And those receptors help to set your internal clock and to get your circadian rhythm back on track.

And this is also what you should aim for: get enough sunlight during the first part of the day. This is crucial to set yourself a strong circadian rhythm. The problem? If you spend most of your time indoors, then you are most likely to only get a fraction of the light exposure you need. To be more precise, it is about 200 times weaker than if you were working outdoors.^​1​

However, if you are like most people, then you are far away from that. In a landmark study, leading chronobiologist Till Roenneberg found out that around half of the population spends less than one hour outdoors during the week. And less than three hours outdoors on weekends. 

That’s far too little to set yourself up for a strong circadian rhythm. Let’s have a look at a little example to add some more details to your cumulative light exposure:

	Indoors	Outdoors, cloudy	Outdoors, sunny
Light intensity	~150 Lux	~10,000 Lux	~120,000 Lux
Time spent	10 hours	1 hour	1 hour
Cumulative	~1,500 Lux	~10,000 Lux	~120,000 Lux
Light-intensive time	0 hours	1 hour	1 hour

For those ten hours indoors, you get practically zero hours to help set your circadian rhythm. And all that time comes in at a marginal 1,500 Lux. Now you spend one hour outdoors. If you are lucky then it’s sunny and you can add a lot of additional Lux. But if it’s overcast it’s a lot less. Either way, you’d only be able to add one more hour of light-intensive time. The crucial time that helps you set your circadian rhythm.

Now you might ask yourself, why two hours? Because in the same study, Roenneberg also found that two hours outdoors are enough to boost your learning capacity, your immune system, your mood, and your social skills.

You will also advance typically your chronotype (the sleep-wake pattern of your circadian rhythm) by one hour. Or, the other way round, your chronotype would be one hour too late and out of sync if you don’t spend at least two hours at outdoor light intensities. In addition, you will boost your learning capacity, your immune system, your mood, and your social skills.

In this post, you can find out all about “What Are Chronotypes and How to Find Out Yours”

How could you achieve those two hours at a high-enough light intensity?

• Walk for a few minutes outside directly after waking up
• Cycle or walk to work (you might even wanna take a detour when the weather is nice)
• Take any and all breaks outside if possible
• Work or study outside if possible

You get the idea, there are plenty of opportunities to increase your time outdoors. And you might be able to come up with even more opportunities that fit your lifestyle. 

Maximize Indoor Lights

#2 Stay as Close to Windows as Possible If You Are Indoors

If you are indoors, always stay next to the windows. Be it in the office, in public transportation, or elsewhere. Even though you won’t get the full outdoor light intensities, you’d still get much more than being even a little further away from it. 

Check out the section below about how to measure light intensities to find out more for your specific case!

Are there more benefits of access to daylight in an office versus being away from windows? I’m glad you asked. Studies found that access to daylight in an office also reduces fatigue^​4​ and increases mood, performance and sleep quality^​5​.

Take Light Showers

#3 Take Artificial Light Showers During the Day If Needed

What would you do if you just can’t get enough natural light? Let’s say, you can’t spend enough time outside. And there’s also no way for you to sit close enough to sunlight.

Your next best guess is to fully boost up your indoor lights. Like to the max and beyond. 

D. H. Avery and colleagues studied the use of bright light in the workplace for thirty patients with subsyndromal seasonal affective disorder.^​6​ Those are the ones who have less energy and motivation during the darker winter months that provide less sunlight. You might also know this as the “winter blues.”

So, what did they do to change it? They treated them with intensive light. Of 2,500 Lux. That might be more than ten times the intensity of what your office has. Some got this treatment during the morning and some during the afternoon.

The result? After two weeks of this light therapy, those patients improved their mood, energy, alertness, and productivity scores, as well as significantly reduced their depression ratings.

And how could you translate the findings from this study (and many similar ones) into your life? Let’s have a look at your two options in the table below:

With lights in your control	With lights out of your control
Let’s say you are fortunate enough to control the general lighting of the building you spend your time in. Or that you would be able to convince the person in charge.	You can’t change your general lighting and/ or you want to get a higher light exposure to reach at least those 2,500 Lux for your personal light therapy.
What should you do?	What should you do?
You should double-check the light intensity of your current lamps. And install lamps with an as-high-as-possible Lux intensity and blue-light-spectrum. They should feel overly bright in the beginning. But don’t worry, your eyes will get used to them quickly.	You should get one or two of those desk lamps that give you individualized light showers. Set them up next to your computer and use them especially during the morning and first part of the day. I’m using two compact sized 10,000 Lux light therapy lamps from a leading health care brand called beurer (you can check them out on their homepage here).

Either way, this is the big takeaway for you: Get more artificial light during the day if you are not exposed to enough natural light.

Don’t Wear Sunglasses

#4 Don’t Wear Sunglasses

At this point, it might be obvious to you that you should get as much light in as possible. Now, if I asked you if you want to further decrease your already too low light exposure, what would you answer me? Correct, a strong no.

However, when you wear sunglasses, you do exactly that: you decrease your precious light exposure. Remember that it is the melanopsin receptors in your eyes that help you get your circadian rhythm back on track? Don’t reduce their light exposure even further through sunglasses.

Get the full overview of how light influences your circadian rhythm in this post about “How Does Your Circadian Rhythm Work”

How much do sunglasses reduce the light that reaches your eyes? They reduce it by a factor of seven to fifteen! That means that for every 1,000 Lux, you only receive between 67 Lux and 142 Lux. With your sunglasses, you can easily reduce the light intensity of a sunny day into an overcast one.^​7​

So, as long as what you are doing is not more dangerous without sunglasses, I’d recommend you not using any sunglasses. 

About the need for sunglasses as sun protection: Your eyes adapt to sunlight just fine. Just as they had for all your ancestors over the millions of years before sunglasses were invented. The cornea and the lenses of your eye, actually filter out a lot of the dangerous UV light before it can cause any damage to your retina. This is your natural sun protection. Just don’t stare directly into the sun. 

For the same reason, don’t wear blue-light-filtering glasses during the day. But let’s get to them into more detail in tip #8.

Spend Time in Nature

#5 Spend a Weekend in Nature

What to do if you mess up your circadian rhythm the whole week long? And there is nothing that you can do about it during the week? Well, in this case, your next best option would be to reset your circadian rhythm during the weekend. With two days in nature.

Ken Wright Jr. from the University of Colorado, Boulder, did exactly this. He and his team sent volunteers camping for a summer weekend.^​8​

But before the trip, they measured their sleep patterns and also the levels of their sleep hormone melatonin. The result? Those volunteers were moderate to late chronotypes. And their sleep hormone melatonin would not rise until 10 pm and only peak after midnight. In short, their melatonin production was delayed. And that made them sleep later, which results in a later chronotype.

Things changed after those two days camping in nature: Their melatonin production went back to normal times and rose between 7 pm and 8 pm. And they became their natural, earlier chronotypes, able to fall asleep before 10 pm. And that after just those two days in nature.

So, if you can’t change your light environment during the week, consider a reset during your weekend. Spend a day or two outside in nature and get in as much natural light as possible. Based on the studies from Ken Wright Jr., this will help you to achieve a shift in your circadian timing that is sixty-nine percent of what you could achieve after a full week of natural light exposure.

Adapt Your Lighting

#6 Adapt Your Home Lighting

In the first part, you have seen how you can increase your light exposure during the day. Now let’s shift gear to your evening and night. As you have seen above, in the second part of the day it is important to reduce your light exposure. Especially your exposure to blue light.

The ideal light for the second part of the day would be light of low intensity and also low in the blue-light spectrum. This combination will least disturb your circadian rhythm. And most help you get it back on track.^​7​

There are two basic options you have here. One, reduce the intensity of your lights. Two, reduce (or better eliminate) the blue-light spectrum of your lights. Or a combination of both at the same time.

Reduce the light intensity	Reduce the blue-light spectrum
Simply dim your lamps if possible or install a dimming switch.	Reduce the amount of blue-light of your lamps if possible.
Have dedicated night lamps that are low in Lux.	Have dedicated night lamps that are amber for the evening or red (least amount of blue-light) for the night.
Use task lights like table lamps (that only falls on the surface) instead of ceiling lights (that falls on everything including your eyes) in the evening.

One quick fix would be LEDs that can dim and change the color, like Philips Hue. These lights could simulate a natural day-night cycle with bright blue-colored light during the day and dimmed amber- to red-colored lights during evening and night. 

Those Philips Hue LEDs are also what I have installed in my bedroom. And they allow me to control both light intensity and light color based on the time of day. With bright blue-heavy lights in the morning and dimmed reddish lights in the evening. Both help to align my circadian rhythm. And both would also help to get your circadian rhythm back on track.

Reduce Blue Lights

#7 Reduce Blue-Light Emissions From Your Screens

Let’s state the obvious first: Your screens are notoriously high in blue-lights and you should reduce the time spent in front of them in the evening and night.^​9,10​ But we both know that that is not always possible. And when the best way of no-screen-time is not available, you can at least reduce the harmful parts of your screens a bit.

How can you reduce the blue-lights? Use your devices to your advantage. Most of them have some kind of night mode already built-in, waiting for you to activate it:

• On Apple devices, activate Night Shift. Go to Settings > Display & Brightness > Night Shift.
• On Android devices, activate Night Light. Go to Settings > Display > Advanced > Night Light.
• On macs, activate Night Shift. Go to Menu > System Preferences > Display > Night Shift
• On computers with Windows 10, activate Night Light. Go to Settings > System > Display > Night Light.
• Alternatively, for macs/ computers, you can download the original player, the f.lux app. This app automatically adapts your display to your time of day.
• On TVs, you might be lucky if you have a rather new model. Many newer models include some kind of night mode, like Samsung’s Eye Saver Mode.

Reducing your exposure to blue-light emitting devices will help you to not disturb your circadian rhythm in the evening and night. It is a crucial step to help you to get your circadian rhythm back on track.

Use Blue-Light Filter

#8 Use Blue-Light-Filtering Glasses

What could you do if you are for one reason or another still exposed to intensive blue lights in the evenings and at night? You could use glasses that filter out those blue light rays that would otherwise mess up your circadian rhythm.

Remember that you have special light receptors in your eyes (called melanopsin) with the only job to tell your brain what time of day it is? And that they are especially sensitive to blue light? That is why filtering out blue light is so beneficial for your circadian rhythm at night.^​11​ 

Just like sunglasses reduce the overall light intensity reaching your eyes, blue-light-filtering glasses reduce the blue-light intensity reaching your eyes. That helps you still use devices at night that emit blue-light rays without disrupting your circadian rhythm.

Here are a few tips about using blue-light-glasses from Satchin Panda, one of the world’s leading chronobiologists:^​7​

1. Only wear your blue-light-filtering glasses for the last three to four hours before going to bed.
2. Don’t wear them during the day. If you have prescription glasses, that means that you would have to get a second pair for only those final hours.
3. Pay attention to the color of these lenses.
   • The orange-pink hue filters out the most blue light.
   • Other colored hue filters out only between five and fifteen percent and don’t really make a difference. Those remaining eighty-five to ninety-five percent of blue light would still be big enough to disrupt your circadian rhythm.

Just to stress it one more time, those blue-light-filtering glasses would weaken your circadian rhythm if you wear them during the day. Since you are most likely not getting enough (blue) light during the day and should not limit it any further. Also, have a look at tip #1 and tip #4 again for more information on that.

Avoid Light at Night

#9 Avoid Any Light at Night If You Can

Do you want to find out the quickest way to disrupt your circadian rhythm? Expose it to bright light at night! That’s why this tip is all about avoiding light at night.

Harvard professor and sleep researcher Charles Czeisler and colleagues studied the impact of light on the circadian rhythm. More specifically the impact of bright light during different day and night times.^​12​

Quick background information: Your body temperature normally has a circadian rhythm and fluctuates about 0.5°C (~1°F) during the day. With its peak in the late afternoon/ early evening and its low point at night.

Ok, back to the study. Czeisler and colleagues measured the body temperatures of healthy volunteers before and after they got their light “treatments.” The result?

The circadian rhythm collapsed for those volunteers that were exposed to bright light between midnight and 2 am. Their body temperature did not follow its normal curve anymore. The result was described “as if their bodies instantly lost track of time.”

Just on the third day, after normal light and darkness exposure, did their body temperature follow its normal curve of their circadian rhythm again.

Want to know what’s even worse about light exposure at night? A group of eighteen leading researchers in their respective fields came together for the National Toxicology Program to evaluate health problems related to artificial light.^​13​

What did they find? Night light exposure may be linked to a host of diseases, including heart disease, metabolic disease, reproductive issues, gastrointestinal disease, immunological disease, and several psychiatric diseases. Ouch!

But what could you do if you need to get up at night and just need to see for a little bit? Let’s use our tips #6-8 here. Use dim red lights. Wear your blue-light-filtering glasses if you need any other lights. And don’t look at any screens. Or at least not at any screens without their blue-light-filtering settings to the max. And you wearing your blue-light-filtering glasses.

Don’t Eat Too Late

#10 Stop Eating Early Enough in the Evening

Do you know what is the worst choice you can make late at night? I mean for your circadian rhythm. It is eating.

You have seen above that light too late disrupts your circadian rhythm. And just like light impacts your internal time in your brain, food impacts the clocks in your organs. To be more specific, any calories consumed impact the clocks in your organs.

Why? Because your body has to go through your digestive process for any calories that you consume. Even those from a tiny snack or a drink. Your body loves calories and wants to have them all. But that also means that it has to start your digestion as soon as calories arrive.

Your organs want to prepare for rest and rejuvenation at night. But with more calories coming in, your metabolism has to fire up again. Then, for the next about two to three hours, your organs have to work on your digestive process. And that cuts short their time to rest and rejuvenate.

Your organs will also need longer to digest those calories at night. Because your organs, especially your gut and stomach, weren’t prepared to digest more calories. These slower-moving calories can then lead to their own set of problems in your digestive system (most prominently acid reflux).

Here is what Professor Satchin Panda has to say about your late-night eating (read: consuming of any kind of calories):^​7​

“Eating late at night is by far the worst choice you can make.”

Satchin Panda

In short, it is significantly healthier and better for your sleep quality if you stop eating early enough in the evening. And like this, you won’t disrupt the circadian rhythm of your organs. Helping you to get it back on track.

Get the full overview of how stopping to eat early enough (and eating for fewer hours every day ) will be one of the best health decisions you can make: “When Is the Best Time to Eat – Based on Your Circadian Rhythm”

Eat for Fewer Hours

#11 Eat for Fewer Hours Every Day

You have just seen that every time you consume calories, your organs in your entire digestive system have to work. And while your organs work they can’t repair and rejuvenate themselves. 

How long is this repair and rejuvenation period? Well, it depends on your eating habits:

• The last calories you consumed determine when your organs can start their repair and rejuvenation process.
• The first calories coming in again stop this process. Your organs have to start processing these calories. Even if that means that they couldn’t finish their repair and rejuvenation processes.

If you are like most people, then you believe that you consume your calories in a twelve-hour window (and are not counting any drinks or late-night snacks). But you actually consume calories for fifteen hours or more. Add the three more hours that your organs need for digestion after your last calories came in and they end up working for eighteen hours or more.^​3​

That means that you make your organs work for at least seventy-five percent of every day. Flip this coin and you see that you are only giving your organs less than twenty-five percent of the time to repair and rejuvenate. Every single day.

Most nutritional science has two general recommendations for you to stay healthy: Eat a healthy diet and don’t eat too much. But timing also plays a crucial role, especially for long-term positive health outcomes. One that is often overlooked.

How crucial is the timing of eating for your health? Let’s have a look at one extreme example first. Let’s have a look at a study Amandine Chaix from the renowned Salk Institute for Biological Studies and colleagues did with genetically identical mice.^​14​

We know that mice become obese, diabetic, and develop other diseases within a few weeks if they have free access to unhealthy food. Food that replicates the standard western diet. That was the first group of mice, the control group. The second group of mice received the same diet and ate the same total amount of calories. But within an eating window of only eight to twelve hours.

The result? Those mice that were in the second, time-restricted-feeding, group were protected from both weight gain and health issues. Even though they ate the same amount of the same food. 

What’s more? When mice those obese and unhealthy mice from the first group were put on a time-restricted-feeding schedule, their diseases could be reversed. Without a change in diet. And without additional medication.

We both know that we are not mice. And as impressive as those results are, you might wonder how applicable they are for you. The short answer is that the results from human studies are promising. Most of them are still focused on weight loss though. But here they were able to confirm that the timing of food intake predicts weight-loss effectiveness. Just like for those mice.^​15​

Now, have a look at the total number of yours that your organs are involved in your digestive process. From the first calories in the morning until three hours after your last calories in the evening or even night. And let’s hear what Satchin Panda, also one of the authors from the mice study above, has to tell you:^​7​

“Look at the total number of hours your stomach is at work. […] If this number is more than 12, here’s the good news: You have something to work on and it will have one of the biggest impacts on your health for the rest of your life.”

Satchin Panda

Your takeaway? If you eat for fewer hours every day then you give your organs more time to repair and rejuvenate themselves. You help get their circadian rhythm back on track.

Get the full overview of how eating for fewer hours every day (and stopping to eat early enough) will be one of the best health decisions you can make: “When Is the Best Time to Eat – Based on Your Circadian Rhythm”

Bonus Tip: Do Exercise

#12 Use Exercise to Help Align Your Circadian Rhythm (Bonus Tip)

The most important ways to get your circadian rhythm back on track are through light and food. More specifically through getting enough light throughout the day and not too much in the evening and at night. And by restricting your eating times to give your organs enough time to repair and rejuvenate.

But then there’s also exercise. Exercise at the right time can also help you to get your circadian rhythm back on track. And at what time would that be? In the morning and early afternoon. Exercising at both of these times can help you to speed up your circadian rhythm and align it closer to your day.^​16,17​

In addition, exercise also influences the circadian rhythm of your muscles.

When you exercise then you increase an enzyme that is involved in the production of a pigment that is also important for your circadian rhythm. You exercise. Your body then increases the level of an enzyme. That enzyme is involved in the production of a pigment. And this pigment is an important part of your circadian rhythm.^​18​

This pigment is called heme. It is in your blood and carries oxygen to all your tissues. And it also tells your internal clock to turn on or off specific genes that are involved in your metabolism. More specifically, your glucose and fat metabolism which your muscles both need to fuel your exercise, along with oxygen.

In this way, exercise directly impacts your muscle clock. And it turns out exercise during both the morning and the late afternoon can help you get your circadian rhythm back on track. And while morning exercise will set you up for a great start to the day, in the afternoon you are at your daily peak performance level. Both are great timings to exercise. And both help you get your circadian rhythm back on track.

Want to find out more about the connection between your circadian rhythm and exercise? Then check out the following post: “When Is the Best Time to Exercise – Based on Your Circadian Rhythm”

How to Measure It

How to Figure out How Close on Track You Are

In the first part, you have seen why you need to get your circadian rhythm back on track. And in the second part, you have seen twelve tips on how you can do so. Based on your individual lifestyle, I do hope that you also already know which of these tips has the biggest impact on you.

Now I want to show you a few ways how you can double-check what you might want to change to get your circadian rhythm back on track.

First, measure your light environment. You have seen above that your perceived light intensity is measured in Lux. And you have also seen that your body wants to receive natural light intensities that are in the thousands of Lux during the day and close to zero at night. At the same time, you are most likely exposing yourself to hundreds of Lux in both cases. Thanks to indoor lighting.

Don’t trust your eyes when it comes to the light intensity of your environment. Your eyes adapt to your light environment and, for most parts, you won’t be able to tell how bright or dark it actually is. 

Step into a dark movie theater and you won’t see much. A few minutes later you are used to the darkness and can see things you couldn’t see before. Step out into the sun and you are blinded and can’t see much either. A few minutes later you can see normal again. 

This adaptation process also makes it so difficult for you to accurately judge the light intensity of your environment. And once you are used to the brightness of a room, you might not notice how it is too dark in comparison to daylight. And too bright in comparison to nightlight. And both messes up your circadian rhythm.

How could you figure out how much Lux you receive at any given time? You could buy a Lux light meter if you want to get precise measures. Or you could get the Lux Light Meter app for your smartphone if you want to get precise enough measures. And that is also what I use. Even though the measures are not as accurate as with a real Lux meter device, they are still accurate enough to give me important information about my light environment. And are direct feedback for me to change things up based on numbers.

Second, calculate your eating timings. Ok, based on the above information (especially based on tip #11) you might already have thought about doing this. If not, I strongly recommend you to start doing so now. At least for a few representative days.

You can simply write down when you take in your first calories of any kind. Then write down when you consume your last calories of any kind. And add three hours that your organs need to process these. The result? The total time your organs need to work on your digestion vs the total time they have to repair and rejuvenate themselves. Aim for at least a fifty-fifty situation.

Third, write down how you subjectively feel. If you are on track with your circadian rhythm, then you should wake up fresh and energized. And without an alarm clock. You will be at your peak both in the morning and afternoon. With a slight dip in between. Yet without brain fog. And you will be able to fall asleep quickly and without any problems.

You can find out more about what it means for you to live aligned with your circadian rhythm in this post about “Why Is the Circadian Rhythm so Important for You.”

Fourth, test and measure yourself. If you have access to test your heart rate, blood pressure, or body temperature, here is what you can look out for. All of those have daily rhythms that are supposed to dip in the evening to prepare you to sleep. And rise again in the morning to prepare you to wake up.

What’s more? Your body temperature normally peaks around the late afternoon. A daily rhythm in your core body temperature is an indicator that you have a strong circadian rhythm. Your blood pressure should go down at night. This is not only an indicator of a strong circadian rhythm but also for a healthy heart.

Personal Experiences

My Personal Experiences

For this part, I have two personal stories to share with you. One involves getting more natural light exposure and the other reducing how much time my organs have to spend digesting food.

Natural Light Exposure

Increased Natural Light Exposure

The less light I am exposed to during the day and the more light I am exposed to in the evening and at night, the later my chronotype becomes. But I never thought what a difference this light exposure has on me.

Do you remember the camping experiment from above? Where students spent a weekend in nature and became around one hour earlier chronotypes? Well, I did a four-month-long “experiment” when I lived in a small Kenyan town called Iten to train with some of the best runners in the world.

Besides running, one of the biggest differences was my daily light exposure. We started running early in the morning, just when the sun came out. Rested and relaxed with direct or indirect sun exposure during most of the day. And then ran again in the afternoon. I was basically exposed to the sun all day long (and never used as much sunscreen before in my life).

As soon as the sun went down, my light exposure also went down dramatically. Just to paint a picture here: There was only one main street with spare lighting. The rest of the town was more or less lit up by the night sky.

How did my chronotype advance? Quite quickly, I naturally woke up some time after 6 am, just before the sun came out. And after the sun went down twelve hours later, it didn’t take me too long to feel ready to go to bed. The sleep I got every night was one of the best ever. I fell asleep virtually as soon as I went to bed and early the next morning I woke up full of energy and ready to start the biggest training session of the day.

Once I was back from Iten, one big learning for me was to implement running sessions before work. And, initially, that went great. Even though I woke up earlier than before, I felt motivated to go out for a run. And energized again once I returned.

But then I got injured on my foot and couldn’t run for a few weeks. And my morning routine of being outside was gone too. While I was initially happy that I could sleep longer, I realized after a bit that I felt worse waking up. The evening before I wasn’t able anymore to directly fall asleep. And my sleep quality overall had become worse. 

My solution? Early morning walks. I started going out for a short ten to fifteen minute walk a few minutes after I woke up. And things changed for the better again. So much so, that I have still been doing those walks on nearly all days without an early morning run. And some work breaks have now also turned into outdoor walks.

Ten-Day Fast

How a Ten-Day Fast Helped Me Sleep Better

In January 2020, I did a ten-day water and tea fast. And one of the more surprising changes I felt was connected to my sleep quality.

A few days into the fasting, I felt how my sleep quality dramatically improved. It was as if my body could finally concentrate on sleeping and sleeping only. I slept for fewer hours than normal, woke up much earlier, and was energized and ready to go once I woke up. Mind you, that was in winter during some of the shortest days. And for the first hours after I woke up, it was still dark.

Well, I obviously connected those changes to not having eaten. And one big learning for me was to stop eating much earlier than normal. 

I had already done time-restricted-eating (aka. intermittent fasting) beforehand, with an eating window between noon and 8 pm. But I never felt that light and ready to fall asleep in the evenings. Rather still full and heavy.

After my fast, I have stopped eating much earlier. Now, I only eat between around 11 am and 3 pm. And I feel much better with it. Especially when it comes to sleeping at night. Unfortunately, my sleep quality is not quite at the level it was during the fast, but it feels much better than beforehand. When I was still eating until 8 pm.

My takeaway for you? Just as in tip #10, stop eating early enough before you sleep. And get the difference between your last calories and when you fall asleep as big as you can. Even if it is just for a few days to try out. Test it out and maybe it has a similar positive effect for you. I, at least, wouldn’t want to change back anymore.

Key Takeaways

Key Takeaways

There are four key takeaways that I want to share with you that all help you get your circadian rhythm back on track:

1. Increase your natural light exposure as much as you can during the day. If that’s not possible, then go for intensive artificial light. And don’t use any glasses that reduce that exposure. (Tips #1 to #5)
2. Reduce your artificial light exposure during the evening and at night. Adapt your LEDs and screens to cut down their light emissions. Use blue-filtering glasses to reduce how much gets through to your eyes. (Tips #6 to #9)
3. Don’t eat for too long and/ or too late. Give your organs enough time to repair and rejuvenate. Stop eating at least three hours before you go to bed. And don’t make food digestion the first task for your organs as soon as you wake up. (Tips #10 and #11)
4. Exercise in the morning and late afternoon/ early evening. Use morning exercise for a great start into your day and exercise in the afternoon when you are at your peak performance. (Tip#12)
   

And now back to you: In which of these areas do you have the biggest room for improvement? And which of these tips will help you most to get your circadian rhythm back on track?

Stay fit,

PS: If you found this information useful, spread the word and help those who would benefit most from it 🙂

References

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