What Are Circadian Rhythms?

There are certain times we feel sleepy and hungry among other aspects of our beings. What decides when we feel so? When we’re told to sleep and wake up ‘on time’, what does it really mean? Why do some people seem to wake up late and work best at night while others are up bright and early and yawning by late evening? The answer to these questions lies in the concept of Circadian Rhythms. So path breaking was this revelation that three researchers were awarded Nobel Prizes in 2017 for their work on the subject.​1​

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Way back in 1729, French Astronomer Jean-Jacques de Mairan observed the daily leaf movements of a certain type of plant. These movements were assumed at the time to be because of changes in the position of the sun, and of temperature. Experiments under constant conditions of light and temperature during which the leaf movements of the plants continued as before, proved that there was an internal mechanism within the plant, independent of light and temperature, that regulated the controlled the movement of its leaves. In fact, an even earlier observation of a similar nature took place back in the fourth century BC.​2​

Here’s the interesting bit. This regulatory mechanism is present at a cellular level, and is present in virtually every living thing on the planet, from single-celled organisms to complex creatures such as mammals, of which us humans are examples.​3​

Circadian rhythms are controlled by a DNA level process within our cells through a mechanism called a transcriptional-translational feedback loop (TTFL); a subject that I won’t elaborate in this article. Having said that the evolution of this internal clock is said to be linked to our dependence on the daylight cycles regulated by the sun. If you’re really interested, you can find a detailed explanation here.​4​

Many types of health events are related to or influenced by the circadian clock, from headaches to heart attacks, including sleep disorders, Alzheimer’s and Parkinson’s Disease and more. The different aspects of our behavior and physiology that are regulated by circadian rhythms include:​5–7​

  • body temperature,
  • metabolism,
  • eating,
  • gastrointestinal health,
  • sleep phases and patterns, and
  • blood pressure among others.

If you’re experiencing health and wellness issues of any sort, I suggest going back to the basics and correcting your sleep cycles. It takes science a while sometimes to back up traditional wisdom – “Early to bed and early to rise makes a man healthy, wealthy and wise”.


  1. 1.
    Callaway E, Ledford H. Medicine Nobel awarded for work on circadian clocks. Nature. Published online October 2017:18-18. doi:10.1038/nature.2017.22736
  2. 2.
    McClung CR. Plant Circadian Rhythms. Plant Cell. Published online April 2006:792-803. doi:10.1105/tpc.106.040980
  3. 3.
    Voigt RM, Forsyth CB, Keshavarzian A. Circadian rhythms: a regulator of gastrointestinal health and dysfunction. Expert Review of Gastroenterology & Hepatology. Published online March 25, 2019:411-424. doi:10.1080/17474124.2019.1595588
  4. 4.
    Kim YH, Lazar MA. Transcriptional Control of Circadian Rhythms and Metabolism: A Matter of Time and Space. Endocrine Reviews. Published online May 11, 2020:707-732. doi:10.1210/endrev/bnaa014
  5. 5.
    Ruan W, Yuan X, Eltzschig HK. Circadian rhythm as a therapeutic target. Nat Rev Drug Discov. Published online February 15, 2021:287-307. doi:10.1038/s41573-020-00109-w
  6. 6.
    Refinetti R. Circadian rhythmicity of body temperature and metabolism. Temperature. Published online April 17, 2020:321-362. doi:10.1080/23328940.2020.1743605
  7. 7.
    Leng Y, Musiek ES, Hu K, Cappuccio FP, Yaffe K. Association between circadian rhythms and neurodegenerative diseases. The Lancet Neurology. Published online March 2019:307-318. doi:10.1016/s1474-4422(18)30461-7

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