Body Clock

Body Clock is referred to an internal mechanism that periodically schedules the body’s activities and functions.

What Is Body Clock?

The body clock is the body’s particular natural timing mechanism that regulates some important biological functions and activities in every living organism. It controls the metabolism, blood pressure, sleep cycle, and even hormone secretion. Researchers 1 explain that it “is the 24-hour internal clock in our brain that regulates cycles of alertness and sleepiness by responding to light changes in our environment.” Also known as Circadian Rhythm 2 , its regulation plays a pivotal role in people’s healthy lives. It coordinates physiological and behavioral activities with environmental variation. This biological clock is composed of some particular molecules that interconnect with the cells of the body. These are connected with and present in every tissue and organ 3 . Researchers 4 have found similar genes in mammals, flies, and some other living organisms that create the clock’s molecular components.

It is considered as the daily cycle which is characterized by a rhythmic alteration in the chemical components level. The rhythmic alteration is addressed as circadian rhythm. This cycle can be observed almost in every living organism. This biological clock is also characterized by the homeostasis of the chemical components. Homeostasis is referred to as a process that every living organism uses for maintaining actively stable conditions for survival. It is also related to the pineal gland 5 and is based on the concept of biological rhythms. The pineal gland is the prime center of the body’s internal clock as it regulates circadian rhythms. It secretes a greater amount of melatonin when it’s dark, this points to melatonin’s role in sleep. Melatonin is the key hormone that plays a central role in the coordination between the circadian system and circadian rhythm. Some external factors such as heat and daylight 6 can directly affect the rhythms.

Understanding Circadian Rhythms

According to a 2014 research paper 7 , our body clock helps to regulate internal cycles related to physiological functions, metabolism, and behavior. It also enables all living creatures to anticipate and understand the rotation of the Earth within the timeframe of 24 hours. “In mammals, circadian integration of metabolic systems optimizes energy harvesting and utilization across the light/dark cycle,” added the researchers. Circadian Rhythm is a part of the body’s internal clock that runs in the background and carries out the body’s important functions and processes. The sleep-wake cycle 8 is one of the most important circadian rhythms. This cycle controls different systems and is synchronized by a master clock in the brain.

Some environmental cues, especially daylight, directly influence the master clock. That’s why the day and light cycle is tied to the circadian rhythms. The circadian rhythms promote restorative and consistent sleep when properly aligned. But it can also create serious sleep problems, like insomnia, when this rhythm is thrown off. Circadian rhythms play a pivotal role in the diverse aspects of mental and physical health. “Circadian rhythms occur in almost all species and control vital aspects of our physiology, from sleeping and waking to neurotransmitter secretion and cellular metabolism,” explains a 2013 study 9 .

The suprachiasmatic nucleus 10 (SCN) is a part of the brain that controls circadian rhythms in different body activities, memory performance, autonomic function, core body temperature, and different behavioral and physiological processes. It is considered as a group of cells in the hypothalamus 11 that respond to light and dark signals. The suprachiasmatic nucleus is also known as the principal circadian clock of the brain. It directs the daily cycles of behavior and physiology. It is the central player in the circadian timing system 12 .

What influences Body Clock

The biological clock is influenced by some behavioral patterns and external stimuli. This clock influences some core activities of the body, which include:

1. Metabolism

The biological clock and food intake are directly related to metabolism 13 . Because it is the only thing that is responsible for energy production.

2. Sleep

This clock controls the sleep-wake cycle, light is considered as the main external stimulus that keeps it set.

3. Age

Aging 14 is also associated with the body clock. This leads to older people experiencing difficulties in completing basic day-to-day activities like energy production, sleep.

4. Food

For synchronizing the circadian rhythms, food is considered as the main stimulus. This clock regulates cellular differentiation and the cell cycle. But the process is not well understood yet.

5. Immune response

During wakefulness, the immune response 15 is very effective. The only need of the body during that time is growing.

6. Physical and mental disorientation

Sometimes the intercontinental and transatlantic travels cause physical and mental exhaustion. Such a condition may lead to disorientation of the biological clock.

Body Clock And Sleep

For functioning properly, every organism requires sleep as it is a vital activity 16 of the body. The homeostatic physiology 17 of the circadian rhythms regulates sleep. Studies 18 have shown that the biological clock and sleep are linked with a hormone named melatonin 19 . This hormone is solely responsible for helping your body fall and stay asleep. Sunlight and darkness affect melatonin production. Our body produces melatonin mostly at night, light influences the body to produce less melatonin during the day. If a person works at night in artificial light, his/her body may produce less melatonin than it needs. People who sleep late or very early have circadian rhythms that are different from most other people. According to a 2018 study 20 , “In humans, dysfunction or misalignment of the circadian clock with environmental cues alters the timing of the sleep-wake cycle, leading to a variety of circadian rhythm sleep disorders.”

Body Clock Disruptions

We can know the role of the biological clock in our health when it gets out of sync. The disruption can happen for various reasons. Disruptions include:

1. Shift Work

Shift work 21 can develop into a circadian rhythm disorder. Most of the night shift workers experience difficulty in their sleep patterns and this affects also the other systems of their body. Sometimes the situation can be chronic too. The reasons behind this connection may involve metabolic changes and weight gain. This condition proves how a lifestyle pattern can affect the system of the body clock.

2. Jet Lag

When people travel across multiple time zones and face difficulties in adjusting to the new schedule due to jet lag, this situation can be considered a biological clock disorder. People experience foggy, sleepy, and disoriented feelings because of jet lag. The reason is mainly the altered time zones.

3. Delayed Sleep Disorder

Delayed sleep disorder syndrome 22 can be observed in people who have a habit of sleeping late at night and due to this, they wake up late in the morning. This disorder can be seen mostly in the young generation who are comfortable in addressing themselves as ‘Night Owls”.

4. Effects of Drugs and Alcohol

Some drugs and alcoholic drinks 23 cause sleep disorders also. Consuming alcohol in the evening may cause unnecessary sleepiness while consuming it late at night may wake up a person later in the night.

5. Irregular Sleep-wake Disorder

People who take short naps throughout the day and have no proper sleeping pattern may experience this disorder. This syndrome 24 can often affect the brain and disrupt the proper functioning of the biological clock.

Treatment Of The Body Clock Disorders

The focus of the treatment is to reset the sleep-wake rhythm. Specialists generally plan the treatment depending on the severity and type of the disorder. The treatments mostly include bright light therapy, melatonin supplement, and healthy lifestyle changes.

1. Bright Light Therapy

In this therapy, the patient is advised to plan a particular time daily to sit in front of a lightbox. The lightbox will provide bright lights like sunlight. Light visors and light glasses are generally used in this therapy. Bright light therapy 25 adjusts the amount of melatonin the body makes to reset the sleep cycle.

2. Melatonin Supplement

Melatonin supplements 26 are considered as the lab-made version of sleep hormones. Specialists prescribe melatonin supplements to treat delayed sleep disorder, irregular sleep cycle disorder, and the like.

3. Healthy Lifestyle Changes

Experts suggest patients follow a daily routine with planned activities. A healthy lifestyle 27 helps in reducing circadian rhythm disorder symptoms. The routine may include a scheduled meal time along with a regular bedtime, daily exercises, avoiding daytime naps, limiting caffeine and alcohol intake, and managing light exposure.

Importance Of A Healthy & Rhythmic Body Clock

It is important to pay attention to how the energy level shifts throughout a 24-hour day. It gives the idea about when a person is at his/her best. It will take some time to adopt a healthy daily schedule to match the body clock, but the changed lifestyle will lead to improved motivation and great productivity.

  1. Reddy S, Reddy V, Sharma S. Physiology, Circadian Rhythm. [Updated 2020 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: []
  2. Farhud, D., & Aryan, Z. (2018). Circadian Rhythm, Lifestyle and Health: A Narrative Review. Iranian journal of public health47(8), 1068–1076. []
  3. Copertaro, A., & Bracci, M. (2019). Working against the biological clock: a review for the Occupational Physician. Industrial health57(5), 557–569. []
  4. Hastings M. (1998). The brain, circadian rhythms, and clock genes. BMJ (Clinical research ed.)317(7174), 1704–1707. []
  5. Binkley SA, Riebman JB, Reilly KB. The pineal gland: a biological clock in vitro. Science. 1978 Dec 15;202(4373):1198-20. doi: 10.1126/science.214852. PMID: 214852. []
  6. Blume, C., Garbazza, C., & Spitschan, M. (2019, August 20). Effects of light on human circadian rhythms, sleep and mood. PubMed Central (PMC). []
  7. Marcheva, B., Ramsey, K. M., Peek, C. B., Affinati, A., Maury, E., & Bass, J. (2013). Circadian clocks and metabolism. Handbook of experimental pharmacology, (217), 127–155. []
  8. Reddy S, Reddy V, Sharma S. Physiology, Circadian Rhythm. [Updated 2020 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: []
  9. Eckel-Mahan, K., & Sassone-Corsi, P. (2013). Metabolism and the circadian clock converge. Physiological reviews93(1), 107–135. []
  10. Pantazopoulos, H., Gamble, K., Stork, O., & Amir, S. (2018). Circadian Rhythms in Regulation of Brain Processes and Role in Psychiatric Disorders. Neural plasticity2018, 5892657. []
  11. Drunen, R. V., & Mahan, K. E. Circadian Rhythms of the Hypothalamus: From Function to Physiology []
  12. Richter HG, Torres-Farfán C, Rojas-García PP, Campino C, Torrealba F, Serón-Ferré M. The circadian timing system: making sense of day/night gene expression. Biol Res. 2004;37(1):11-28. doi: 10.4067/s0716-97602004000100003. Erratum in: Biol Res. 2004;37(2):357-8. PMID: 15174302. []
  13. Froy O. The circadian clock and metabolism. Clin Sci (Lond). 2011 Jan;120(2):65-72. doi: 10.1042/CS20100327. PMID: 20929440. []
  14. Duffy, J. F., Zitting, K. M., & Chinoy, E. D. (2015). Aging and Circadian Rhythms. Sleep medicine clinics10(4), 423–434. []
  15. Scheiermann, C., Kunisaki, Y., & Frenette, P. S. (2013). Circadian control of the immune system. Nature reviews. Immunology13(3), 190–198. []
  16. Lichtenstein G. R. (2015). The Importance of Sleep. Gastroenterology & hepatology11(12), 790. []
  17. Gnocchi, D., & Bruscalupi, G. (2017). Circadian Rhythms and Hormonal Homeostasis: Pathophysiological Implications. Biology6(1), 10. []
  18. Cajochen C, Kräuchi K, Wirz-Justice A. Role of melatonin in the regulation of human circadian rhythms and sleep. J Neuroendocrinol. 2003 Apr;15(4):432-7. doi: 10.1046/j.1365-2826.2003.00989.x. PMID: 12622846. []
  19. Tordjman, S., Chokron, S., Delorme, R., Charrier, A., Bellissant, E., Jaafari, N., & Fougerou, C. (2017). Melatonin: Pharmacology, Functions and Therapeutic Benefits. Current neuropharmacology15(3), 434–443. []
  20. Farhud, D., & Aryan, Z. (2018). Circadian Rhythm, Lifestyle and Health: A Narrative Review. Iranian journal of public health47(8), 1068–1076. []
  21. Wickwire, E. M., Geiger-Brown, J., Scharf, S. M., & Drake, C. L. (2017). Shift Work and Shift Work Sleep Disorder: Clinical and Organizational Perspectives. Chest151(5), 1156–1172. []
  22. Nesbitt A. D. (2018). Delayed sleep-wake phase disorder. Journal of thoracic disease, 10(Suppl 1), S103–S111. []
  23. Roehrs, T. A., & Roth, T. (2015). Sleep Disturbance in Substance Use Disorders. The Psychiatric clinics of North America38(4), 793–803. []
  24. Blythe, J., Doghramji, P. P., Jungquist, C. R., & And others. (2009, December). SCREENING & TREATING PATIENTS WITH SLEEP/WAKE DISORDERS. Boston University. []
  25. Zhu, L., & Zee, P. C. (2012). Circadian rhythm sleep disorders. Neurologic clinics30(4), 1167–1191. []
  26. Tordjman, S., Chokron, S., Delorme, R., Charrier, A., Bellissant, E., Jaafari, N., & Fougerou, C. (2017). Melatonin: Pharmacology, Functions and Therapeutic Benefits. Current neuropharmacology15(3), 434–443. []
  27. Farhud, D., & Aryan, Z. (2018). Circadian Rhythm, Lifestyle and Health: A Narrative Review. Iranian journal of public health47(8), 1068–1076. []
Scroll to Top