Unraveling the secrets of our circadian rhythm

Thursday, October 12, 2017. Author Dr. Haran Sivapalan

Unraveling the secrets of our circadian rhythm

We at FitnessGenes would like to congratulate scientists Jeffrey Hall, Michael Rosbash and Michael Young for winning the 2017 Nobel Prize in Physiology or Medicine. The trio were awarded the prize for unpicking the genetics of our ‘circadian rhythm’ – or ‘body clock.’ Without their ground-breaking work, we would not be able to analyze your CLOCK gene, tell you whether you’re more likely to be a night owl or a morning lark, or advise you on when best to work out, eat, or drink coffee.

What is your circadian rhythm?

My colleague Sarah Barron has written a great article about this very topic. To recap: a circadian rhythm is any biological process that intrinsically cycles over a 24-hour period. We have an internal body clock deep in our brain that sets our circadian rhythms. Circadian rhythms influence everything from when we naturally sleep and wake, to when we produce certain hormones and when we feel hungry. 

What did the scientists discover? 

•    Period gene and PER protein

Studying fruit flies, the team first identified one of the genes responsible for circadian rhythms – the ‘period gene’.  Like fruit flies, humans also have period genes. As you may know, genes, which are sections of DNA, typically encode proteins – large molecules that have a variety of functions in the body. The period gene encodes a protein called PER.

What’s special about the PER protein is that its levels in the body, like sightings of Batman, increase during the night, but decrease during the day. In other words, the amount of PER expressed goes up and down in a cycle. And there are no prizes (Nobel or other) for guessing how long each cycle takes – it’s 24 hours. The inner workings of our biological clock were being prized open.

But that’s only part of the picture. The question remained – how and why does the level of PER protein oscillate in a cycle? As the scientists discovered, the PER protein acts to inhibit the period gene – thereby slowing down its (PER’s) own synthesis. It’s a classic feedback cycle.

As levels of PER increase during the night, the activity of the period gene becomes blocked. In turn, this reduces the production of PER protein throughout the day. With less PER protein around to block the period gene during the daytime, the gene’s activity increases and it gradually produces more PER protein. In turn, this causes levels of PER to accumulate during the night, restarting the cycle. 

•    Double time and timeless genes

The Nobel Laureates also discovered two other genes central to the circadian rhythm. One of these was called ‘timeless’ - a gene that helps the PER protein get into the cell’s nucleus to inhibit the period gene. The other gene was ‘doubletime’ – a gene that delayed the build-up of PER protein, setting the biological clock to restart every 24 hours. The names of genes excepted, it’s all very ingenious and, in my opinion, a testament to the beauty of nature. 

And what about the CLOCK gene?

Your CLOCK (Circadian Locomotor Output Cycles Kaput) gene regulates the level of PER protein in cells and thereby influences your circadian rhythm. At FitnessGenes we test for different variants of the CLOCK gene, which can determine whether you’re raring to go in the morning or, like Batman and me, much more of an evening person.  

One version of the gene, the ‘C’ allele, is linked to a preference for evenings, but, on the other side of the coin, a higher risk of sleep deprivation. Appetite and bodyweight are also affected by your circadian rhythm, with studies showing carriers of the ‘C’ allele finding it more difficult to lose weight.

If you want to know which version of the CLOCK gene you carry and how best to eat and exercise to sculpt a ‘timeless’ physique, get your DNA analyzed by FitnessGenes.

I hope you enjoyed this story.  Please read my other blog post Just Say No to Upselling, which was recently quoted on Inc.com


1)  Young, M. W., & Kay, S. A. (2001). Time zones: a comparative genetics of circadian clocks. Nature reviews. Genetics, 2(9), 702
2)  Valladares, M., Obregon, A. M., & Chaput, J. P. (2015). Association between genetic variants of the clock gene and obesity and sleep duration. Journal of physiology and biochemistry, 71(4), 855-860.

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