Biological clock adjustment

Key Insight

● I slept 8 hours and barely woke up, and afterwards I was tired? How many times have you heard or said this? What’s the problem? Very likely your biological clock. Due to modern life our eyes do not receive enough natural/sunlight to reset the clock. We spend too much time indoors, when we go outside we wear sunglasses, at night we are exposed to bright artificial light, and our bodies are totally confused. When to sleep and when to be awake? The answer through evolution is that the sun was the only reliable light source, so our circadian rhythm is tuned to a 24‑hour cycle. For thousands of years the first cue to wake was the first rays of the sun, so our body adapted to that and releases more cortisol about 12 hours after waking to wake us and adjust the clock to release melatonin after about 12 hours. If there is no signal, or it occurs at 2 pm you can easily see what problems can arise. Statistics say only 15% of people wake up well rested before the alarm (I’m among them now, but not long ago I wasn’t). The vast majority of people who think they are night owls merely have poorly set biological clocks. Recently there is a lot of scientific research showing a deep link between light exposure/darkness and mental health.

● Therefore people who work shifts, and frequently cross time zones, put their bodies under great stress and seriously jeopardize their health because their bodies are in a constant state of confusion. We owe a huge thank you to these people who perform very important work for society.

● Light - the most effective way to set our biological clock. Ideal light is the light our bodies are best evolutionarily adapted to (sunlight/daylight). Our bodies expect to see bright light when outside during the day, and to not see bright light when outside at night. How to achieve this? ○ Immediately after waking at the time you want to get up, in the first 30–60 minutes, expose your eyes to daylight for 5–15 minutes (stand up forcibly for the first few days if needed). This is easiest with a light morning walk or time spent on an open balcony. Light entering through a window is usually not strong enough, but when we are outside, even on a cloudy day, there is enough light to trigger morning cortisol. Of course this does not mean looking directly at the sun if it’s bright outside (you should never do that), but letting some morning sun into the eyes is good, especially in early morning sunlight near the horizon. Also exposing to daylight at sunset helps set the biological clock, so it would be good to spend some time outside then as well (in the morning is more important; if possible just one priority, focus on that). Exposing to sunlight during peak sun hours is not good for the skin and should be minimized or use UV protection. Since I started this practice my morning caffeine craving is minimal. Like sleep and calories, our body has a “calorie/tonne” accounting system for light exposure, so on cloudy days you need to stay outside a little longer, and on sunny days a bit shorter. ○ To aid this process your bedroom should not have curtains or blinds that block light. Natural light should be allowed to enter the sleeping room as much as possible. ○ Exposure to bright light, especially bright blue light after sunset should be avoided. Evolutionarily, blue light came only from the sun, and it remains the signal by which the body adjusts the clock. Red/orange light came from fire and the floor and our body learned to ignore it. Here we recommend using apps that turn off blue light after sunset (f.lux and nightshift) on your electronic devices as well as dim floor lighting in warmer colors after sunset. Glasses blocking blue light are also an option, however I’ve found apps sufficient and I don’t need glasses.

● Body temperature - another signal for adjusting the biological clock. When we are awake our body temperature is higher, and when we sleep it is lower. Roughly 2 hours before the usual wake time our body temperature is at a minimum, and about 6–8 hours after the usual wake time our body temperature is at a maximum. Vigorous physical activity and exposure to cold raise our body temperature, while exposure to heat (hot shower or sauna) lowers it (yes, opposite). If we want to move the biological clock forward (wake earlier) we should do activities that raise body temperature before the temperature maximum, and activities that lower temperature after the maximum, ideally before sleep.

● Special needs - it may be that your biological clock needs to be set differently from the sun. Aligning with the sun is healthiest, but we can keep it set to another time if needed (for example if we work in another time zone). Essentially the same principles apply as above, just in case you want to wake later we do the opposite. We expose ourselves to bright blue light in the evening (as many hours after sunset as we want to shift), we have physical activity and stimulants in the evening, and push the daylight exposure to a later time.

● Flying and changing zones - Your biological clock has been brought into 100% alignment with your time zone, but you may travel far where the time zone difference is large. What then? ○ If it’s less than 7 days it’s not worth changing zones; sleep by your own zone. If you usually go to bed at midnight and wake at 8 am in your time, calculate what that is in the new time and continue doing it at the same time. You will probably need to shield yourself from daylight, but it’s not worth adjusting to a new time zone for such a short trip. ○ If you must fly it’s better to fly during the day. Even if you can fall asleep on the plane and sleep for 8 hours in one go, that sleep will be of very poor quality for many reasons. With good preparation the time spent on the plane can be very productive (since there’s almost no internet the best flow sessions happen on the plane. I use earplugs + noise‑cancelling headphones at the same time to fully mute the noise). ○ If you travel long distances adjust your biological clock gradually to the new time zone using the above methods by 1 hour per day. Here you can speed up the process with melatonin (taken 9 hours before the desired wake time). You can start this process in your current zone a few days beforehand (if I travel west I start shifting downward and waking later; if I travel east I do the opposite).