Circadian Rhythm
An Overview and Why It Matters
A circadian rhythm, as the name ‘circa-dian’ implies, is a daily cycle every living organism goes through (yes, even plants and bacteria). For most of those organisms, and definitely for us humans, the cycle enters into a phase of rest (in fact, sleep) as the sun sets and into a phase of activity as the sun rises.
We’ve followed this rhythm for millennia, and every single cell in our body takes some cue from the rhythm. Influencing biological systems and processes like:
- Sleep-Wake Cycles
- Hormone Secretion
- Metabolism
- Core Body Temperature
- Cognitive Performance
- Immune Function
- Cell Repair and Growth
- Mood and Mental Health
- Gut Microbiome
- Muscle Strength and Physical Performance
Even in the hunter gatherer days, we would make sure to find a cave to sleep in at night time. Early civilisations like the Greeks and Egyptians would use sundials to tell the time. Relying on exactly what the Sun was doing to structure their day. We obviously still base our clocks on the movement of the Sun, with daylight saving coming into play to keep that aligned as much as possible.
This rhythm will still be active in completely dark, controlled environments.
In 1962, French geologist Michel Siffre isolated himself in caves for two whole months to study his internal clock. He was in total darkness with no access to clocks, sunlight, or other time cues. Despite the absence of external light, his body maintained a sleep-wake cycle that averaged slightly over 24 hours, confirming the body’s intrinsic circadian rhythm.
Throwing this pattern out of rhythm causes many negative health effects, especially if done chronically and irregularly. Studies have been done on mice where they were mutated to no longer have a circadian rhythm. These mutant mice were abnormally hungry all the time and ended up obese, they also had altered glucose metabolism and a predisposition to diabetes.
Nowadays, a misaligned circadian rhythm is more common than one that’s not. Artificial light exposure, screen use at night, irregular sleep schedules, shift work, travel, and lack of natural daylight all contribute to widespread issues spanning any of the circadian processes in the body.
The first step you can take to start getting it under control, while counter-intuitive is going to end up with you having better sleep and more energy in the long run.
Wake up at the same time every day, and go outside.
Waking up at the same time daily, even on days off. Allows your body to start latching onto to the 24 hour cycle. Combining that with a bedtime at least 8 hours before that waking time is then the obvious next step.
Getting into a cycle like this, one that doesn’t change, will mean you start getting sleepier around your bedtime and actually able to fall into deep, restful, high quality sleep. Which is just as important for health as consistent training and solid nutrition.
Finally going outside, assuming the Sun is up at that time, provides your body with the ‘zeitgeber’ (time-giver) it needs to set the circadian clock. On top of the benefits of fresh air, being outdoors and starting your day away from work. Light in the eyes is the main way your brain knows what the time is, making sure you receive a large dose of lux into your eyes right after waking will ensure your rhythm stays stable – even when it has to change due to shift work or travel.
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