The Clock Genes Within Us and Zeitgeber: The 2017 Nobel Prize in MedicineCategory: Chronobiology / Circadian Rhythms

When cave explorer Michel Siffre descended into an ice cave in the French Alps in 1962, he had neither a clock nor a calendar with him. His aim was to see how human perception of time would change when completely isolated from the outside world. Siffre lived in pitch darkness for weeks. He turned on the lights when he woke up, ate his meals, and slept when he felt sleepy. The results were staggering: Although there were no external stimuli, Siffre's body managed to maintain a rhythm of approximately 24 and a half hours.

This experiment proved the existence of a clock operating deep within our biology. However, this clock needs to be "reset" every day and adapt to the outside world. This is where that fascinating term of German origin comes into play: Zeitgeber.

The Spirit of Time: What is Zeitgeber?

Zeitgeber, meaning "Time Giver" in German, is any environmental cue that synchronizes our biological clock with the real time in the outside world. If our internal clock—our circadian rhythm—is a wristwatch, Zeitgebers are the atomic towers that update this clock with a radio signal every morning. We are biological machines trapped in the planet's rotation. The strongest Zeitgeber is undoubtedly Sunlight. But not just light; a heavy dinner eaten in the evening, a strong coffee in the morning, even the dog walk we take at the same time every day are all time signals shouting "This is the time!" to our cells.

The massive tour the Earth takes around its own axis determines not only the sky but also the rhythm of a hidden orchestra governing every cell from your hair strand to your toe. Your body is actually a colossal factory where millions of tiny biological gears are interconnected. The most important feature of this factory is that it knows what to do on its own without looking at the clock outside. However, there is a relay race that continues incessantly inside this giant factory, and four special hero proteins play the leading role in this race.

Day and Night Teams

Imagine millions of tiny clocks working ceaselessly inside your body. These clocks determine when you will get hungry, when you will get sleepy, and how you will wake up with energy in the morning. There are two main teams for this factory to work properly.

1. The Day Team (BMAL1 and CLOCK) When the sun rises in the morning, these two friends hold hands and start work. You can think of them as the morning chefs of the factory.

• What do they do? They enter the cell and shout "Wake up!" They give energy to your body, allow you to focus, and order other workers to "Prepare for the evening, produce PER and CRY proteins."

• Concrete Example: The moment morning sunlight touches your eyes, these chefs get to work immediately. It is thanks to them that you feel energetic.

2. The Night Team (PER and CRY) This duo, produced throughout the day, multiplies thoroughly when evening comes. They are the night watchmen of the factory.

• What do they do? Their numbers increase so much that they go and sit next to the morning chefs (BMAL1 and CLOCK) and prevent them from working. They say, "Okay friends, enough work for today, now it's time to rest." They inhibit the day team, dim the lights, and put the metabolism into repair mode.

• Concrete Example: When you start getting sleepy in the evening, when your eyelids get heavy, PER and CRY proteins are actually whispering "Go to bed!" to your body.

What Happens If These Clocks Break?

Imagine you flew to the other side of the world and got Jet-lag, or played with a tablet all night and were exposed to blue light. The blue light of the tablet tricks your brain. Your brain thinks there is sun outside, and the night watchmen (PER and CRY) cannot do their duty because BMAL1 and CLOCK still think it's daytime.

This confusion disrupts the order inside the factory. The result? You feel tired in the morning as if you haven't slept at all because the night team in the factory couldn't finish its job of repair and recovery.

A Small Tip: If you want to help these tiny workers in your body:

• Open the curtains immediately when you wake up in the morning: Wake up the Chefs.

• Put the phone away an hour before going to bed at night: Let the Watchmen work.

We have come a long way since Michel Siffre's cave experiment. We now know that we are not just living beings, but also "time-breathing" beings. Respecting our Zeitgebers is not just about sleeping better, but reconnecting with the biological nature of being human

2025 Study: Can Opening Your Windows Protect You From Diabetes?

This molecular clock theory we have been talking about for years took on flesh and bone with an exciting study published in 2025. A new research in the journal Cell Metabolism proved how these four hero proteins (BMAL1, CLOCK, PER, and CRY) manage not only our sleep but also our blood sugar like an orchestra conductor.

Researchers scrutinized one of modern man's greatest delusions: Living between four walls, under artificial lights. In the experiment, some individuals with Type 2 diabetes were placed in spaces receiving natural daylight, while others were in rooms with standard office light. The results showed once again that we should not underestimate the power of the biological clock.

The Findings:

• Blood sugar levels of those living under natural light followed a much more balanced course than those remaining in artificial light.

• Natural light entered as the strongest Zeitgeber and woke up the sleeping "day chefs" (BMAL1 and CLOCK).

• When these chefs got to work, the body's insulin resistance began to break, and cells decided to use sugar much more efficiently as fuel.

• Energy Preference: The bodies of individuals whose biological clocks were synchronized with natural light became much more inclined to burn fat instead of sugar for energy.

This current research whispers this to us: Living in harmony with our biological clock instead of stubbornly resisting it can be a weapon as powerful as drugs in the fight against chronic diseases. Just opening the curtains, going out to the balcony in the morning to look at the sky, or taking a short walk during the lunch break is enough to reset that Nobel Prize-winning clock in your cells.

In the future, medicine will perhaps offer not only prescriptions but also "light and timing" guides. Until that day, the best thing to do is to give the chefs of that enormous factory inside you the only thing they need—natural light—and keep the factory clean.

(Reference: Natural daylight during office hours improves glucose control and whole-body substrate metabolism. Cell Metabolism, 2025)