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How to reset internal clock: Can You Change Your Circadian Rhythm?

What Is A Circadian Rhythm And How To Reset Your Body Clock?

Humans have clock genes that make the body tick like a well-oiled machine. Learn about your circadian rhythm and how it affects your health and disease risks.

A circadian rhythm is a 24-hour biological clock that affects your sleep, digestion, and metabolism. When your circadian rhythm is disrupted, it can even increase your disease risks.

The circadian rhythm is a body clock that organises all the biological processes necessary for life. It is dictated by clock genes that trigger essential metabolic activities, like storing energy, transporting oxygen, getting rid of waste, and releasing hormones and neurotransmitters.

Table of contents

  • What is a circadian rhythm?
  • How the circadian cycle works
  • Do you need to reset your body clock?
  • Circadian rhythm and health
  • How to fix your sleep schedule

Even though you can’t see or feel this clock, circadian health is essential for your health and wellbeing. In this article, you’ll discover what happens when the cycle rhythm is disrupted, how to reset your body clock, and how to fix your sleep schedule.

What is a circadian rhythm?

How does your body know what time it is? (Ted Ed video)

The circadian rhythm is a 24-hour clock that dictates millions of invisible metabolic processes that keep the body alive. It determines digestive rhythms, fat burning and fat storage, sleeping patterns, and much more. This biological rhythm is run by clock genes that signal when each process should take place.

Approximately 20% of genes turn on and off during the 24-hour cycle.

Going to bed late, playing with your phone at midnight, eating late in the evening, and working night shifts are all factors that can shift your circadian cycle. Scientific evidence now indicates that circadian rhythm disruptions are associated with serious, but preventable, chronic diseases like diabetes type II, heart disease, obesity, stroke, and cancers.

How the circadian cycle works

A circadian rhythm chart can help you optimise your daily activities

The circadian rhythm is made up of a set of clocks and a central “master clock”, called the suprachiasmatic nucleus (SCN). The SCN is located in the hypothalamus, the part of the brain responsible for regulating stress, reproduction, and growth hormones. It also indirectly impacts sleep hormones.

The body’s clock contains about 20,000 cells, which are located just above the intersection of the optic nerves. The cycle rhythm is set by signals from special melanopsin cells in the retina in response to light exposure. Blue light (from bright daylight, phone screens, and TVs) has the strongest effect on melanopsin receptors, followed by green and red light.

The circadian rhythm reacts to light: it wakes you up, and it puts you to sleep by triggering cascades of chemical events in your brain.

Body clock genes have been discovered in nearly every organ of the human body. These genes turn on and off at predictable times, switching on and shutting down the production of proteins that perform essential functions within the body’s cells.

Interestingly, studies show that blind mice and blind people still have active melanopsin receptors that regulate their biological clock. This helps to explain why patients suffering from blindness can “sense” light, even if they can’t see it.

Find out more about your genes☝ Take the Atlas DNA Test to explore how your genetic make-up affects your health and wellbeing.

Do you need a body clock reset?

Sleeping at irregular times, using devices, eating late at night, and other pernicious habits displace the cycle rhythm. When a person’s biological cycle isn’t on schedule, it causes a wide range of minor health issues that can affect everyday life.

Low energy, mood swings, food cravings, weak immunity, and having trouble losing weight are common side effects of circadian disruption according to Professor Satchidananda Panda, author of the Circadian Code.

AreaCommon problems
SleepDifficulty falling or staying asleep, sleeping too much
WeightWeight gain, inability to lose weight
VitalityLow energy, reliance on caffeinated products
DietLate-night food cravings, stomach cramps & indigestion
MoodDepression, emotional outbursts & irrational anger
ImmunityWeak immune system, frequent illness & infections

Circadian rhythm and digestion

The digestive system secretes the most gastric juices, enzymes, and hormones in the first half of the day. This activity reduces as the afternoon progresses into evening. These molecules are all essential for healthy digestion, which is why eating late at night can cause indigestion.

Circadian rhythm and sleep

Your circadian rhythm is run by clock genes

At night, the circadian rhythm is focused on putting the body to sleep, removing waste products, and repairing tissues from the wear-and-tear of daytime activities. In fact, sleep is the only time for the brain to remove the waste products of chemical reactions.

When you mess with your sleep schedule, or deprive yourself of sleep, you impair the brain’s ability to operate at maximum efficiency.

Circadian rhythm and disease

Living out of sync with the body’s circadian rhythm over the short and long term is associated with serious, chronic, and preventable diseases that affect the body’s metabolism, according to a 2016 systematic review on the “Interaction between circadian rhythms and stress”.

In one referenced study, the human participants with impaired circadian rhythm function had “higher blood glucose and insulin levels as well as elevated blood pressure, which are markers for metabolic and cardiovascular disease.”

The study’s summary of its effects on night shift workers demonstrated that such professionals have “a higher incidence of obesity, diabetes type II and related metabolic disturbances along with hypertension (high blood pressure), coronary heart disease, and ischemic stroke”.

How to fix your sleep schedule

Light and darkness are the main determinants in circadian rhythm. When daylight or screen light is detected by your eyes, it sends signals to the suprachiasmatic nucleus, which regulates all the clock genes in your body.

To reset your body clock, you need to put yourself on a schedule that respects your body’s metabolic rhythm. While this may be impossible for night shift workers, it is an achievable goal for people with day jobs.

  • Go to bed and get up at the same time every day.
  • Turn off TV screens, phones, and tablets 1-2 hours before bed.
  • Eat your biggest meal early in the day when digestive juices are highest.
  • Stay away from caffeinated beverages in the afternoon and evening.
  • Cut down on alcohol at night because it affects sleep quality.
  • Stop eating at least 3 hours before bed to avoid indigestion.
  • Get blackout curtains and dim light bulbs for your bedroom.
  • [Sachin Panda, The Circadian Code]
  • Koch C.E. et al., Interaction between Circadian Rhythm and Stress 2017
  • S. Panda et al., Coordinated Transcription of Key Pathways in the Mouse by the Circadian Clock
  • Blue light has a dark side
  • Circadian rhythms fact sheet
  • Thomas C. Erren et al., Shift Work and Cancer 2010
  • Bennett J.E. et al. (2018). NCD Countdown 2030: worldwide trends in non-communicable disease mortality and progress towards Sustainable Development Goal target 3.4
  • NHS Prevalence, Achievements and Exceptions workbooks 2016

How to reset your internal clock to combat jet lag

A few simple measures can help minimize the sleep disturbances and malaise that can occur when you cross several time zones.

Image: faithiecannoise/iStock

This month we perform the annual ritual of turning back our clocks as Daylight Savings Time ends. Most of us can handle the one-hour time change easily. However, when we travel long distances across several time zones, few of us can survive the trip without feeling a little out of whack. For holiday travelers flying from coast to coast or overseas, recovering from the symptoms of jet lag—fatigue, insomnia, digestive upsets, and headaches—can consume a day or two of precious vacation time. According to Dr. Charles A. Czeisler, director of the Division of Sleep Medicine at Harvard Medical School, jet lag is due to a misalignment between the external environment and the internal clock in the brain that drives our daily performance, alertness, and the ability to sleep.

What happens during jet lag

Minimizing jet lag

If your destination is only a zone or two away, you may need to make only minor adjustments, like eating meals, going to bed, and awakening a little earlier or later than usual. If you’re crossing several time zones, you may want to try the following:

Gradually switch to the new time. For several days before you leave, move mealtimes and bedtime incrementally closer to the schedule of your destination. Even a partial switch may help.

Stay hydrated. During the flight, drink plenty of fluids, but not caffeine or alcohol. Caffeine and alcohol can dehydrate you, which worsens the symptoms of jet lag. They can also disturb your sleep.

Switch your bedtime as rapidly as possible after arrival. Don’t turn in until it is bedtime in the new time zone.

Use the sun to help you readjust. If you need to wake up earlier at your destination, get out in the early morning sun. If you want to rise later than you do at home, wait to go out in the sun until late in the afternoon.

A quick fix for jet lag?

In 2009, Dr. Clifford Saper and colleagues at Harvard-affiliated Beth Israel Deaconess Medical Center identified a second “master clock” in mice that can regulate circadian rhythms when food is scarce. In essence, the body’s circadian rhythms are suspended to conserve energy.

It’s been theorized that humans may have a similar mechanism and that a brief fast may trigger a quick reset of circadian rhythms. Dr. Saper has suggested a 12-hour to 16-hour fast the day before and during travel. For example, if you were to take a flight from New York City to Honolulu, you would refrain from eating for couple of hours before take-off and during the flight, but would have a good meal as soon as convenient after landing. This technique hasn’t been tested in clinical trials, but there are many testimonials in the media to its effective-ness.

If you want to try this, it’s a good idea to check with your clinician to see if it’s advisable for you. And you will still need to drink water—not caffeinated beverages, juice, or alcohol—during your flight.


what it is and how to get enough sleep

We are controlled by circadian rhythms. This biological clock affects how we sleep, expend energy, and digest food.

Let’s figure out how to make friends with them.

Our sleep schedule and activity schedule, and well-being in general, are subject to daily cycles. Therefore, sometimes, no matter what we do, it can be difficult to get ready for work in the afternoon or force ourselves to go to the gym in the morning.

In this article, we will figure out how to make friends with your biological clock in order to use it to your advantage.


  • 1. What are circadian rhythms
  • 2. How Our Internal Clock Works
  • 3. How circadian rhythms affect our health
  • 4. Why it is dangerous to disrupt circadian rhythms
  • 5. How to reset your internal clock
  • 6. Note

What are circadian rhythms

Circadian rhythms are the human biological clock. They set the rhythm for all vital processes in the body. The body clock is determined by genes that start and stop metabolic processes, such as storing energy or releasing hormones.

24 hours

how long does one biological clock cycle last on average

About 20% of all our genes are “turned on” and “off” during one complete cycle.

The main mechanism of the biological clock is the suprachiasmatic nucleus (SCN) of the hypothalamus. This part of the brain is responsible for the response to stress, sexual behavior, coordination of actions and other important functions.

This nucleus receives information from light-sensitive cells of the retina and other receptors and based on it synchronizes the work of biorhythms .

Approximately so biological processes follow each other during the day

Also, the suprachiasmatic nucleus informs the pineal gland and the endocrine gland when it is time to produce the sleep hormone melatonin.

Melatonin concentration increases in the evening, peaks at night and decreases during the day.

A with another important hormone, cortisol , the reverse story.

Photo by Jamie Street / Unsplash

Its concentration rises in the morning, when we need to be alert, and decreases in the evening, when we start to feel sleepy.

How our internal clock works

The genes responsible for the operation of the internal clock are called period and timeless . Their activity fluctuates throughout the day and is regulated by a feedback loop mechanism. As soon as the level of proteins encoded by these genes reaches a certain level, the synthesis of these proteins stops. The level drops – synthesis resumes.

Sleep and wakefulness are affected by light

Light and its absence are the main, though not the only, regulators of circadian rhythms.

Cold blue light from office lamps, computer screens, TVs and smartphones disrupts these rhythms. As a result, the body “thinks” that daylight hours are in full swing. Red and green light also negatively affect the course of the internal clock.

Circadian rhythms are “turned on” and “turned off” by light. Bright artificial light triggers cascades of chemical reactions and disrupts the correct daily routine.

Human circadian rhythms are not a separate organ, they cannot be seen or felt. But they are necessary for health and normal life – and persist even in many blind people.

Photo by Max van den Oetelaar / Unsplash

If you watch TV shows at night, eat late and heavy dinners, work the night shift and go to bed at dawn, the coordinated work of genes and circadian rhythms is disrupted. Some metabolic processes start later than usual, while others stop altogether.

How Circadian Rhythms Affect Our Health

Night shifts can increase cancer risk – disrupted circadian rhythms make it harder for the body to prevent tumor formation.

The International Agency for Research on Cancer has even classified shift work as a carcinogen.

Working with a constant night schedule rather than a hopping schedule may be less dangerous in this regard.

Photo by Kartabya Aryal / Unsplash

Scientists have linked circadian rhythm disturbances to serious but preventable diseases: type 2 diabetes, cardiovascular disease, obesity, stroke and cancer.

To understand how these diseases develop, we need to look at what happens when we break our sleep hygiene.

  • How circadian rhythms affect digestion

The gastrointestinal tract produces the most enzymes, gastric juice and related substances in the first half of the day.

Therefore, it is advisable to have a hearty breakfast, but have a light supper.

Also in the morning the peristalsis works most actively. If you eat heavily at night and wake up late, the risk of constipation, colic, bloating and indigestion increases, because the digestion process slows down.

Taking care of your digestive health is easier with the Atlas Microbiota Test. You will learn how diverse the composition of the bacteria in your intestines, whether there are enough beneficial bacteria, and how the microflora protects you from diseases. How circadian rhythms affect the brain

Photo by Konstantine Trundayev / Unsplash

This fluid removes metabolic products, including toxic compounds that impair memory function. Also, during sleep, myelin sheaths are actively restored – they are needed to transmit signals between neurons.

Sleep phase disruption interrupts these important processes.

As a result, we wake up tired, lethargic and not ready for serious intellectual work.

If you constantly ignore your biological rhythms, this can lead to neuropsychiatric disorders.

  • How circadian rhythms affect disease risk

Insomnia, lack of sleep and poor sleep quality lead to hypertension and insulin resistance, which increases blood glucose levels. These symptoms signal metabolic disorders and diseases of the cardiovascular system.

Studies show that people who work night shifts are more likely to suffer from obesity, type 2 diabetes and hypertension.

The risk of developing these diseases is also increased in people with disturbed circadian rhythms.

Why disrupting circadian rhythms is dangerous

Poor sleep quality brings other, less obvious problems. A sleepy person easily gains weight and hardly loses it.

He crave sweets and junk food more often than healthy food, because the body tries to compensate for the lack of energy with cravings for simple carbohydrates.

Also, if jet lag becomes more difficult to fall asleep and wake up, addiction to caffeine develops.

Photo by Nathan Dumlao / Unsplash

I want to sleep as long as possible, but sleep stops replenishing my strength.

The risk of depression increases, there are mood swings during the day and bursts of negative emotions. And the body becomes more vulnerable to diseases and infections.

How to reset your internal clock

The good news is that a broken body clock can be repaired.

Together with the correct daily routine, you will return to productivity and healthy sleep. Restoring your circadian rhythms and daily routine doesn’t mean going to bed right after sunset, especially if you’re a night owl.

The main thing is to avoid artificial light and fall asleep during the time period when melatonin is produced, that is, from 12 am to 4 am.

Avoiding gadgets an hour or two before bed will help you fall asleep easier. Also in the evening it is worth turning on lamps with warm dimmed light instead of bright fluorescent lamps. To restore the sleep pattern, you need to go to bed every day at about the same time, even if it is a day off.

If you often feel tired and distracted during the day and do not sleep well, you may have thrown off your biological clock. Here’s what will help bring everything back to normal:

  • If you really need to check social networks before going to bed or watch a movie on your tablet, turn on the night mode – with it, the backlight becomes yellowish and less bright.
  • Switch from visual content to audio before bed: listen to podcasts and audiobooks.
  • Avoid alcohol in the late evening – it impairs the quality of sleep.
  • Go to bed slightly hungry.
  • Buy heavy, light-blocking curtains and open them as soon as you wake up.
  • In the afternoon, choose decaffeinated drinks.
  • Use ear plugs and a sleep mask if outside noises or street lights interrupt your sleep.

Genetics can also influence sleep patterns: for example, insomnia can be inherited. To identify the genetic predisposition to insomnia and the characteristics of caffeine metabolism, you can use the Atlas Genetic Test.

More interesting articles about sleep on the Atlas blog:

  • Sleep, diet, and giving up your smartphone: habits that will make you happier
  • Night work: dangers and health benefits
  • Sleep and microbiota: how appetite and digestion are related to sleep quality
  • Sachin Panda, The Circadian Code
  • Koch C. E. et al., Interaction between Circadian Rhythm and Stress 2017
  • S. Panda et al., Coordinated Transcription of Key Pathways in the Mouse by the Circadian Clock
  • Blue light has a dark side
  • Circadian rhythms fact sheet
  • Thomas C. Erren et al., Shift Work and Cancer 2010
  • Bennett J.E. et al. (2018). NCD Countdown 2030: worldwide trends in non-communicable disease mortality and progress towards Sustainable Development Goal target 3.4
  • NHS Prevalence, Achievements and Exceptions workbooks 2016
  • The role of sleep and wakefulness in myelin plasticity
  • Night shift work, short sleep and obesity

Do you want to stay young? Repair your biological clock

Komsomolskaya Pravda

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and about new research revealing the secrets: how to stay alert and healthy

” Repair “of the biological clock will allow us to stay young and healthy for a long time.

At the international conference “Genetics of Aging and Longevity”, which recently ended in Sochi, experts spoke about new research that reveals the secrets of how to keep fit and healthy


When people talk about the biological clock, people usually think of the sleep-wake cycle, but this is not quite the right idea, – says Cleveland Biology Professor University (USA) Roman Kondratov. Together with colleagues, the scientist explores the mechanisms of aging and ways to slow it down in order to prolong a healthy, active life as much as possible. As it turned out, the biological clock is one of the main means that allows our body to maintain good health and look young. We are talking about a whole system of genes and proteins that work in such a way that all processes in the body of humans and animals occur in a certain rhythm. During the day, our pulse, pressure, body temperature, and metabolic rate change. This mode allows the body to painlessly endure changes in the environment, including the change of day and night, weather, and food breaks. As long as the biological clock works efficiently and without failures, we are young, vigorous, look good and can successfully resist many dangerous diseases.


– Experiments were carried out in the laboratory: they deliberately disrupted the work of the biological clock in mice, destroying one of the proteins of this harmonious system, – says Professor Kondratov. The results were disastrous: the rodents began to age rapidly. In humans, a similar process occurs: with age, individual genes and proteins – the “cogs” of the biological clock – fail, disrupting the vital system. The body loses its defenses, begins to grow decrepit, heart disease, blood vessels, diabetes, cancer, Alzheimer’s disease (senile dementia) develop.

However, scientists also conducted another optimistic experiment. In adult mice, the production of one of the proteins responsible for the work of the biological clock (sirtuin-1 protein) was increased. And life expectancy has increased! Now, in several laboratories around the world, research is underway on methods and drugs that would allow you to safely repeat a similar effect on other animals, and then on humans. MIT biology professor Leonard Guarante is reassuring that by adjusting the biological clock (circadian rhythms), the body can rejuvenate and cope with a number of dangerous diseases, including diabetes and severe inflammation that develop in old age.

But the main goal and perspective is to slow down the aging process itself. By keeping the body younger and healthier, we thereby prevent age-related diseases, including diabetes, cancer, heart attacks and strokes.


Of course, one has to live to see the appearance of “medicines for old age” in pharmacies. Experts’ forecasts on this matter differ: someone is sure that the first revolutionary drugs for people will become widely available in the next 5-7 years, someone takes 10-15 years. At the same time, now we ourselves, with our own hands, can both improve and maintain the normal functioning of our biological clocks, as well as knock them down and loosen them ahead of time, accelerating the approach of old age.

– The most important thing for strengthening biorhythms is regularity , Roman Kondratov explains. – Imagine a swing: in order to swing properly, you need to push them, “feed them”, strictly periodically, and if you push inappropriately, they, on the contrary, will stop.

Studies show that the biological clock runs longer and works best if you go to bed, get up and eat at the same time every day. Moreover, surprisingly, the diet turned out to be an even more effective factor than the change of day and night, experts emphasize. That is, having breakfast, lunch and dinner at the same time is especially important for establishing all the biorhythms in our body. As for sleep, the period from 12 a.m. to 4 a.m. is the peak of melatonin production, one of the most important anti-aging hormones. So this time is definitely worth spending in bed. In general, according to scientists, people who sleep an average of 7-7.5 hours live the longest.


Jet lag is our enemy

Many have heard about the dangers of jet lag – the jet lag syndrome, when a person quickly moves on an airplane at a “different time” of day and night. Often, such drops are accompanied by insomnia, headache, and indigestion. And – they beat on our biological clock, forcing them to rebuild the work of the whole organism.

“However, few people think that similar “mini-jet lags” are voluntarily and regularly arranged by the majority of people,” notes Professor Kondratov. This happens when, after a week of work, accustoming the body to wake up at 7 in the morning and have breakfast at 8, we drastically change our regimen on weekends: we go to bed and get up later, we eat at different hours. The price for such relative pleasure is the loosening of the biological clock and the acceleration of aging.


Do protein diets shorten life?

A few years ago, scientists proved that if experimental animals are put on a diet with limited methionine (an amino acid that is part of many proteins in meat, milk, and cheese), then health improves and life expectancy increases. Recently researchers at Harvard Medical School made a new discovery that reducing methionine at the same time as restricting other amino acids in the diet works best.

Biologists explain that when the body receives a lot of amino acids from protein food, then cells grow and divide actively. In childhood, this is good, but in adulthood it already goes sideways: when the body and organs have formed, further growth accelerates aging. If cells do not receive enough amino acids (protein food), they do not spend resources on growth, but concentrate on protecting the body, resisting stress and infections. This slows down aging.

In the course of the research, another important regularity was revealed: if the food is rich in other proteins, then limiting only methionine is useless. Moreover, it can harm the body. Therefore, for example, athletes who eat a lot of protein foods are not recommended to reduce methionine.

Scientists are now working on the creation of an “ideal” diet, which will select the optimal proportions of proteins, fats and carbohydrates, based on the latest discoveries.


What takes our years

Last week experts from the Public Chamber of Russia discussed the problem of combating aging. Experts noted that today a person is able to live 90-100 years. But in practice, this period is reduced due to several main reasons.

– Bad ecology.

– Wrong diet (violation of the regimen, fast food, eating before bed).

– Lack of sleep (sleep less than 7 hours).

– Sedentary lifestyle.

– Alcohol abuse, smoking.

– Poor quality medical care (inaccurate diagnosis, untimely treatment, medical errors).

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