Always tired? How your internal clock can influence your sleep

If you are wondering why you feel tired, limp and exhausted all the time during the day, even though you are getting enough sleep, then you need to take a closer look at your internal clock. Just getting enough sleep is not enough, it has to happen at the right time. Because our organs and body functions follow harmoniously coordinated and very individual internal rhythms. If you constantly live against your internal clock, there is a discord between these body’s own rhythms, which in the long term can even upset body functions such as your digestion or your cardiovascular system. On the other hand, if you first know which “chronotype” you are,

In this article you will learn:

  • What the terms “internal clock”, “chronobiology” and “chronotypes” mean
  • How your body controls and regulates your sleep-wake cycle
  • What causes disturbed inner rhythms can have
  • What health consequences it can have if you live permanently against your internal clock
  • What simple measures you can take to live in harmony with your internal clock

Sleep-wake rhythm and the internal clock

What is ticking inside me – how our body finds its rhythm

Our life is subject to the constant rhythmic alternation of day and night, light and dark, within 24 hours. Our body functions also have their own internal clock , which is adjusted to this daily change and has thus adapted to the consequences of the earth’s rotation in the course of evolution.

Regardless of body temperature, blood sugar level, heartbeat, pulse rate, blood pressure or hormones such as growth or thyroid hormones – all functions change depending on the time of day . For example, while your body temperature drops in the evening to prepare for sleep, your heart rate increases in the morning so that you can start the day fit and active.

Chronobiology deals with this phenomenon of the temporal organization of biological systems and their regularities . Put simply, it is the doctrine of the internal clocks of all living beings.

While your body recovers during the night, repairs tissue and breaks down unwanted substances in the brain and body, during the day it is geared towards physical activities and the use of previously stored energy. Researchers refer to this body’s own rhythm as circadian , as our internal clock follows its own rhythm of around 23-25 ​​hours.

Compared to normal time, it is usually a little behind or a little ahead and is only synchronized with our daily rhythm through external influences , so-called timers. The most important timer is the natural 24-hour light-dark change . But our social contacts, physical activities or the time of our meals also reset our internal clock every day. Depending on when these timers act on our internal clock, they can support or disrupt the natural rhythm.

The internal clock, which in particular determines our sleep-wake rhythm , consists of many different body rhythms and is controlled by a higher-level control center in the brain , the so-called nucleus suprachchiasmaticus.

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He directs the cyclical production of numerous biologically active substances and various hormonal glands , including the pineal gland, also known as the epiphysis. This is where the hormone melatonin is produced, which is released as a sleep hormone, especially in the dark and in the evening, and signals to your body that it is now time to rest. If daylight falls on certain receptors on your retina in the eye in the morning, melatonin production is reduced again.

A Nobel Prize for the internal clock

In 2017, three US researchers received the Nobel Prize for Medicine for their research on the internal clock. Since the 1980s, they have been deciphering the mechanisms that control circadian rhythms. They found out that various so-called clock proteins are produced in a rhythmically oscillating manner and broken down again, thus ringing in day and night. With their work they laid the foundation for further research on the internal clock.

Why you should know your own chronological rhythm

How exactly our individual internal clock ticks is genetically determined . However, this rhythm changes in the course of our lives and controls how much sleep we need, for example as babies, adolescents, adults or senior citizens.

In general, science distinguishes between two so-called chronotypes , the characteristics of which are influenced by genes, gender, age and the environment:


As a “lark”, i.e. morning type, you usually wake up early in the morning and are quickly productive and in top shape . However, you get tired again earlier in the evening and often go to bed early. So early school or working hours are very convenient for you.


If you are an “owl”, i.e. an evening type, you are often wide awake late in the evening and can concentrate well. Since you usually need more time in the morning to really get going, early working hours are more of an horror to you . During the day you often feel tired, in a performance hole and as if you had slept too little.

Most people are so-called normal types who are somewhere between these two extremes and tend in one direction or the other.

If you’re struggling to get going in the morning, you’re probably the evening type.

In extreme cases, however, sleep-wake patterns can change to such an extent that, for example, as a result of leaden tiredness, normal participation in social and working life is no longer possible . The causes often remain unexplained at first. Then, together with a sleep specialist, you need to look for ways and means to gently influence your own circadian rhythm in such a way that a normal life becomes possible again.

If you ignore your own rhythm in the long term and live against your internal clock, this can have significant consequences for your health. Sleep and concentration disorders , a weakened immune system with a higher susceptibility to infections, but also digestive problems such as constipation can be possible consequences if we live permanently against our internal clock.

With or against the internal clock? – You decide!

When lark days meet owl clocks

The change between day and night is the most important external timer that calibrates our internal clock to a 24-hour rhythm. The most important internal timer is the previously described hormone melatonin. An ongoing conflict between our everyday life with the corresponding timers and our chronotype leads to a kind of chronic social jetlag .

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Owls, i.e. evening people who have to start their everyday family or work life very early in the morning, know the phenomenon that it is very difficult and slow to get going in the morning. Early risers, on the other hand, can often demonstrate better school performance at a young age, but owl types often compensate for the morning sag with more creativity and curiosity.

If you live against your own internal clock, it can also lead to significant sleep disorders. Such disturbed sleep-wake rhythms are now even recognized as diseases in which your sleep takes place almost at the wrong time.

The internal clock and the sleep phase syndrome

In the so-called sleep phase syndrome, there is a permanent shift and thus disruption of the sleep period. As a healthy person, you get tired at a time that is normal for you (for example around 10-11 p.m.) and go to bed, only to wake up and get up again at around 6-7 a.m. in the morning. In the pathological state, the bedtime shifts so dramatically forwards or backwards that participation in social working life is hardly possible any more due to severe fatigue. In the international classification system for diseases, they are classified as forward (ICD-9 CM 780.55-0) or backward (ICD-9 CM 780.55-1) sleep phase syndrome.

Since our digestive system and our intestinal microbiota are also subject to a circadian rhythm, your intestines often react sensitively very quickly if you live against your internal clock. You should therefore always take complaints such as  constipation very seriously and treat them accordingly.

If you live permanently against your internal clock, symptoms such as constipation can occur.

In the long term, disturbances in our circadian rhythms can even increase the risk of metabolic diseases such as diabetes. Corresponding connections have long been suspected in cancer, neurological and mental illnesses. 

Find the rhythm with your own internal clock

You may be wondering whether owls and larks can even be helped if their daily rhythm does not match their own internal clock . After all, it’s genetically determined, isn’t it?

In fact, the internal clock cannot simply be reprogrammed in such a way that it fits into an opposing daily routine. You’re an owl or a lark. But if you know and accept this, then it becomes much easier to adapt your behavior during the day so that it fits your very individual chronotype much better. So what can you do

As a first step, you should try to determine your chronotype as precisely as possible . When are you at your best? When do you usually get tired? Over a period of around two weeks, pay attention to when your performance and concentration highs are during the day and derive your chronotype from this. Usually there are hardly any surprises, because many people know whether they are a “morning grouch” and “night owl” or rather an “early bird”.

In the second step, you should share your findings with your fellow human beings . Of course, it is not always possible for your family and colleagues to follow your chronotype completely. But maybe there are colleagues who are currently a different chronotype with whom you can coordinate well. The lark is in top shape in the morning and takes over the early meetings, the owl is still efficient at the meetings in the late afternoon – a situation that your boss may also be happy about.

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If possible, coordinate with your colleagues to adapt your daily work to your chronotype.

Thirdly, there is a chrono-hygienic schedule of the day . If you know your high and low phases, you can adjust your everyday life accordingly. In low phases with little creativity, you can do standard tasks. For physical activities and sports, you should also try to find the most convenient time of day for you. Make sure that exercise can also have an impact on your sleep and should therefore be more moderate, especially in the evening hours. With gentle measures such as alternating showers, on the other hand, you can help to get going much better in the morning or with power naps, i.e. short sleep of no more than 30 minutes, to bridge short fits of fatigue.

If you need to take medication, make sure it is timed as well, as its side effects can also make you tired or awake. Avoid exposing yourself to artificial light from screens or mobile devices about an hour before bed. Instead, use the time for relaxation exercises and try to tick off worries that are bothering you before going to sleep, if possible. Pay attention to these and other rules of good “sleep hygiene”. You can also contribute to a chronoharmonic day with your diet , for example by avoiding very fatty or spicy foods if you want to sleep soon afterwards.

Chrononutrition – nutrition by the clock

The so-called chrononutrition is about eating in harmony with the body’s own enzyme release. For example, fats should be absorbed particularly well by the body in the mornings and mornings. However, hard scientific facts are lacking. Chrononutrition is often confused with intermittent fasting.

Incidentally, even your intestinal flora, also called gut microbiota , follows a circadian rhythm. Your intestinal bacteria react very sensitively to hormonal changes in your body and receive numerous circadian signals via the so-called intestinal-brain axis.

In fact, you can contribute to it yourself and decide whether you live with or against your internal clock. In addition, the individual chronorhythm usually changes over the course of a lifetime.

Do you find it difficult to fall asleep or sleep through the night? We give you 20 tips for healthy sleep !

Always tired? How your internal clock can influence your sleep

Even when we get enough sleep, we can be tired, broken, and drained. Because the time for our sleep must also be the right one . Our internal clock determines the rhythm that is individually determined for each of us, when we are most productive during the day and when we need rest and relaxation. This rhythm also dictates how much sleep we usually need. Changed sleep rhythms that collide with this internal clock can even make us sick in the long run . Digestive disorders such as constipation, concentration disorders, irritability or susceptibility to infections are then not uncommon. With the right lifestyle and a few simple measures, you can find your way back to your own internal clock.

Sources and further reading

Breus, M. Good timing is everything: the right time for sleep, food, sex and almost everything else. Goldmann Verlag, 2017. ISBN 978-3442176625

Roenneberg, T. How we tick: The importance of chronobiology for our life. DuMont Buchverlag, 2018. ISBN 978-3832161880

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