Daylight & Your Body Clock



Whether you realise it or not…


Your internal “body-clock” influences most of the decisions and actions that you take every 24 hours.


That includes, but is not limited to…


  • when you feel hungry

  • when you feel tired

  • when you wake up

  • when you focus/work best

  • when your body physically performs at it’s best

  • when your digestion is at it’s most optimal


The purpose of your body clock is to help ensure that your lifestyle follows the “ideal” 24-hour pattern as much as possible…


Theoretically this would help to maintain/improve good health.

Hundreds/thousands of years ago, your body clock would have followed the natural cycle of day/night fairly accurately.


Some people have a slightly ‘earlier’ body clock, others have a slightly ‘later’ clock (“Morning people” vs “night-owls”).

A number of cues tell your body/brain what time of the day it is, and what your body should be optimised to do at that time.

The key one, is daylight.

We have evolved to be awake and fully alert during daylight hours.


And sleep when it's dark.

But feeling awake or tired is far from being the only response to the daily cycle.

And ‘confusing’ the body clock has many significant consequences for your health & well-being.

For example, not getting enough sleep due to not falling asleep at the ‘right’ time and still having to get up for work the next day.

So it is clearly important to maintain an accurate body clock.

Waking Up & Going To Bed

In most cases, you’ll wake up in the morning (things will be different for shift workers etc).

This will usually be to the sound of an alarm clock…


In other words, you have an unnatural wake-up.

Already, you are fighting against your natural body-clock.

Nonetheless, you have a series of decisions to make, immediately, which will affect your clock for the rest of the day and tomorrow…

Early daylight exposure: Do you wake up to daylight, or darkness?


This will obviously depend on the time of day that you have to wake-up, and also the time of year. But it’s important to get exposed to daylight as early as possible after waking.

Daylight ‘confirms’ that it is daytime and that you are supposed to be awake.


As well as reinforcing the fact that your body needs to start feeling less tired, a countdown towards falling asleep again should begin in the morning...


Your brain expects to be asleep again in approximately 16 hours.


Delaying the start of the internal countdown, means that you will probably find it harder to get to sleep ‘on-time’ that the end of the day.

So failing to get light exposure in the morning can confuse your body clock, disrupting these processes...

Get the blinds open (or lights on if it is still dark outside*) and get moving.


Early in the morning is a relatively good time for caffeine (if you already drink it).


(Although if you feel that you need caffeine to wake-up, you probably aren’t getting enough quality sleep in the first place).

*the majority of indoor lights don’t come close to replicating daylight. But this would still be preferable to dim lights or darkness.

Winding Down: Just as daylight helps to kick-start your body and brain in the morning… darkness (should) help to switch things off later in the day.

In reality, at this point, you are probably substituting bright screens for daylight.

Laptops, phones, TVs etc will automatically produce ‘blue light’ which as far as your brain is concerned, is the same as daylight… hence the confusion for your body-clock.

Ideally, if you want to be asleep at 10pm, you’d want to start winding down at least a couple of hours beforehand…

  • no caffeine

  • no daylight

  • less food/fluids

  • no screens

By watching TV, scrolling through Facebook etc…

You are sending more confusing signals to your brain. Those signals tell you that it is daytime and you’re supposed to be awake/alert.

If you routinely struggle to get to sleep… despite knowing that you need to sleep...

These late night habits may be (at least partly) to blame.

During The Day


Light is measured in “Lux”.

The higher the value, the brighter the light.

Outdoors, a sunny, summer day will provide more than 100,000 lux.

Even a cloudy day will provide more than 1000 lux.

However, a typical office, “well-lit” with standard artificial light will provide less than 500 lux.

So… if you work indoors, the part of the day when you are supposed to be at your most awake and alert…

You are only getting a tiny fraction of the light that you would be in daylight.

Another confusing signal for your body-clock… your brain interprets this as sunset and makes you feel tired.

If this sounds familiar, simply try to follow the day/night cycle as closely as possible;

  • daylight/bright light as early as possible after waking up

  • maintain as much exposure to daylight as possible throughout the day (sit near windows, get a daylight lamps, take breaks outside etc)

  • avoid ‘blue light’ at night. Either reduce screen time completely or switch device

  • settings to “Night Mode” which reduces blue light.

  • maintain discipline – go to bed at the right time!




You Won't Beat Evolution....


Your body is the result of millions of years of evolution...


Your internal body-clock is hardwired into your system.


You cannot (permanently) override this...


At least not without significant health consequences.

For optimum performance (physical & mental)...


Work with your body-clock.


Not against it!