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Sleep play an important roles to our health and body fat levels. However yet many people disregard this fact and deprive our body from a good night's sleep. A stable circadian rhythm is the big factor in achieving a quality sleep. A century ago, there is no such things called a disrupted circadian rhythm due to the simple reason of our light sources were restricted after sunset.

In modern days, we stare at a brightly lit screen which held inches away from our face, well past sundown. Is our mobile phone really affecting our health to such an extent that we're becoming sicker fatigued and fatter? And if a mobile phone has such an effect on our health, what about the TV's and computer screens in every corners of our life? Could something as simple as blocking blue light solve an obesity crisis? 

How Blue Light from Modern Days Technology Are Destroying Your Precious Sleep

Humans being need sleep. We die if we stay awake and don't sleep for 10 days. Studies have shown that one third of American adults are chronically sleep deprived. Deprived of sleep can affects us negatively. It affects our memory, creativity, immune system, muscle repair, inflammation, hormone levels, and our body fat levels.

Deprived of quality sleep is often related to higher fat levels, obesity, and higher cortisol hormones. Excess cortisol resulted in accumulation of excessive belly fat. Hormonal disruption plays a huge role in causing fat gain not only simply due to deprive sleep.

A lot of people suffer from insomnia or unable to have quality, uninterrupted sleep which cause us feeling drained in the morning.

If you are suffering from poor sleep, you’ve likely have tried all sorts of methods such as herbal teas,  meditation, or sleep medication. Unfortunately, some people even have to rely on drugs to achieve their nightly state of Zen.

This shouldn’t be the case. Our bodies should get the desired sleep.

So what’s the possible cause of all these sleep issues? Can it be due to high amounts of caffeine? Work related stress that keep us awake whole night? These could some of the causes. However there’s something even bigger than the stimulants or stress. It plays an important role in our lives, affecting far more than just our sleep. In fact, it affects every cell in our body, our immune system, our mood, and our hormones. What holds such power?


Light as Waves

When one thinks of light, they normally would imagine the visible light which enable us to see. When we switch on a light, this produces light (and other forms of energy such as heat). But there is a lot more to light than the colours of the rainbow that we known. Visible light is only a small part of the electromagnetic spectrum.

This spectrum is a range of frequencies or varying wavelengths of energy. Visible light makes up a very small part of the electromagnetic spectrum

There are more to light that travelled to your eyes than the visible light your eye seen.

In this article, we are going to discuss on the visible light spectrum ranging from about 390nm to 700nm. The changing of light wavelengths causes us to see different colours. These varying wavelengths also causes different effects on our body.

How does light affect mood, hormones, and more importantly, sleep? It’s all about disrupting your circadian rhythm.

Circadian Rhythm

The term circadian rhythm originates from the Latin words circa (meaning approximately) and diem (day). The most obvious circadian rhythm is the sleep-wake cycle, though other circadian rhythms exist such as rhythms in body temperature, hormones release, and even gene expression.

Circadian rhythms differs in each individuals, but on average, the length is 24 and a quarter hours. Night owls typically have slightly longer circadian rhythms, while early birds have shorter ones.

  Source -

Circadian rhythms affect more than simply tell our body when to sleep or awake; they also affects the hormones released in our body.

Hormones are very powerful things. If circadian rhythm is disrupted in your body, it can cause our body to release cortisol late at night instead of first thing in the morning. This would leave you feeling groggy in the morning and wide-awake late at night. 

So how do our body and circadian rhythm keep track of time? The same method like humans do - by using clocks! Scientists have found that nearly every cell in the body are able to keep track of time.

Venice Greenwood from Quanta Magazine explains it like this:

“Every 24 hours, responding to a biochemical bugle call, a handful of proteins assembles in the cell’s nucleus. When they bind to each other on the genome, they become a team of unrivaled impact: Under their influence, thousands of genes are transcribed into proteins. The gears of the cell jolt into motion, the tissue comes alive, and on the level of the organism, you open your eyes and feel a little hungry for breakfast.”

These cell clocks or should be more correctly refers as circadian clocks function by responding to light and darkness from the suprachiasmatic nucleus located in the hypothalamus. Functions that are regularly carried about in the body can be traced back to the cell’s circadian clocks.

Take for example our hair cells. They divide at a particular time every evening. Our liver releases enzymes to assist digestion at meal time (which is why I recommend eating at consistent times every day), and our body prepares for sleep in the evening - that is, assuming these clocks are functioning properly!

By understanding how our body keeps track of time, it’s easier to understand how the circadian rhythm impacts our hormones, how we feel and how we perform. Our body likes and yearn for routine. Can you now understand why our felts horrible after travelling across multiple time zones?

It’s All About Cycles

The body functions on cycles. Some functions happen at night, while others function during the day. When one is healthy, the body clocks are in sync and the body's activities properly coordinated.

Any disruption to this coordination will leads to a feeling of perpetual jet lagged, but also:

  • Higher rates of cancer
  • Diabetes
  • Heart disease
  • Obesity
  • Insulin resistance (leading to diabetes)
  • Leptin resistance

Memory and learning inhibition are also often linked to disruption to circadian rhythms. This is why resetting circadian rhythm may be the most effective way of improving sleep and health.

Most of us have experienced how long haul flights disrupted our circadian rhythm. However there is a multitude of other factors that can disrupt our circadian rhythm. A study published in Science Translational Medicine discovered that “caffeine at night delays the human circadian clock”.

Researchers discovered that 200mg of caffeine which equivalent to a double espresso intake 3 hours before bedtime can resulted in a 40minute phase delay in the test subjects’ biological clocks. They showed that caffeine had a direct effect on the internal clocks in human cells.

No doubt that drinking coffee in the night can affects sleep. This same study, however, had an interesting finding that was overlooked by the media.

The researchers tested how caffeine affected circadian rhythm, they also looked at the light. The result of research shown that bright light will cause delays to one’s circadian rhythm much more than of a double espresso does.

Stone Hearth Newsletters reported the following on these findings:

"Bright light alone [...] induced circadian phase delays in the test subjects of about 85 minutes.” Double that of the caffeine-drinking group.

You didn't read wrongly. Bright light can delayed the circadian rhythm by twice as long as a double espresso.

Light and Its Impact on Circadian Rhythm

Our body is constantly receiving signals from environment. One of the most vital, yet often disregard signals is that of light or the lack thereof. If we go back to the year 1878, before light bulb was invented by Thomas Edison, Light sources were limited to fire (candles) and the moon once sunset.

There were no such thing as TVs, smart phones, digital alarm clocks, or even a blinking LED from a smoke detector! The body’s exposure to light past sundown was extremely low.

Comparing with hundreds of thousands of years of human evolution and adaptation to environment, 150 years is only a split of second. Our bodies lived in light and dark cycles. In the dark, we are restricted to low-light activities such as reading, writing, talking, having sex, and obviously, sleeping. When the sun was up we fished, hunted, gathers, played, and worked.

Our bodies and circadian rhythm has evolved based on this light-dark cycle. Modern days, 138 years after the invention of the light bulb, our bodies are still programmed to function in this light-dark cycle.

For example, it has been shown that exposure to morning bright sunlight assists to reset our body circadian rhythm, especially if it has been disrupted. Therefore if you are traveling, try to get morning sun light exposure when arrive at your destination. For a night owl with poor sleep habits, morning sunlight exposure will help to address your sleep issues. 

If you’re thinking that instead of going outside every morning to get morning light exposure, you’ll just turn the lights on in your room, you are very much at the wrong direction. Sun light and artificial light are not the same. It’s all about lux. Lux is a measure of light brightness as seen by the human eye.

For comparison, moonlight is about 1 lux. A brightly lit office is about 400 lux. An overcast day is about 2,000 lux. A spring day is about 40,000 - 60,000 lux. Bright summer sunlight is about 120,000 lux! The level of magnitude is incomparable, thus why getting outside is so important. This does not include the beneficial effects of UV exposure on the skin.

Lastly, Body senses light not only through the eyes but through the skin. In fact, vitamin D is synthesized in the liver and kidneys through the skin’s exposure to UV-B light. So when you’re outside, be sure to expose as much skin as possible.

Blue Light and Melatonin

What is the connection between light, circadian rhythm, and sleep? The answer is melatonin.

Melatonin is a hormone secreted by the pineal gland in response to darkness. It is commonly referred to as "the sleep hormone," but it also plays a vital role in controlling inflammation levels in our body while aiding our immune system (this is why, if you have a few nights of insufficient sleep, you’ll often catch a bug or become run down). It achieves this through its antioxidant properties. 

Melatonin is produced by our body after about 4 hours of darkness and generally peaks around 2am.

It runs opposite to cortisol: when melatonin is high, cortisol is low in this state, you should be sleepy. When melatonin is low, cortisol is high, you should feel alert and energised for the day. A good picture of this relationship can be seen here:
 Source -

Melatonin is also the connected to sleep and fat loss, as melatonin causes leptin to be released during sleep. Leptin (the hormone that causes you to feel full after a meal) enters the hypothalamus, your thyroid is up-regulated, your metabolism increases, growth hormone is released, and the body burns fat.

Circadian dysfunction is connected to obesity and it appears that leptin is the key. Researchers are finding that circadian clock deficiency or chronic jet lag leads to leptin resistance, and leptin resistance creates hormonal irregularity and fat gain.  This is the body fat that, no matter how hard you train or how strict your diet, just won't go away. Hormonal cycles are crucial not only for sleep but for maintaining a healthy weight. 

As we outlined above, light, and blue light in particular affects our circadian rhythm. Light influences melatonin secretion, with blue light having a far greater impact than red light.


Modern LED and fluorescent lights contain high amounts of blue light. Researchers who created this chart also tested how each light sources affected melatonin, and found that high levels of blue light had the greatest effect on melatonin suppression. Brightness was also a determining factor. 

There’s an excellent site called fluxometer that shows you the light output of various devices, ranging from the iPhone to streetlights. I recommend heading over there and playing around. It will also show how bright the light from a device is compared to daylight, and the resulting circadian rhythm phase shift. Here's a screenshot from the iPhone 6 report.

Takeaway: Light exposure at night shuts down melatonin production with blue light having a huge impact compared to red light. Blue light sources include modern light bulbs, computer screens, cell phones, and TVs.

You can probably guess how. In a nutshell, it involves:

  • Increasing exposure to blue light and UV light in the morning and middle of the day
  • Decreasing exposure to blue light and UV light in the evening and at night.
Who would have thought? Expose yourself to the sun when the sun is up and avoid light (artificial light) when the sun is down!

Let’s look at some practical steps to help us make this a reality.

Increasing light during the day:

  • Get outside within 30 minutes of waking up. Aim to maximise skin and eye exposure to the sun. This means no glasses and ideally, your shirt off. Twenty minutes is a good amount, but even 5 minutes will be beneficial.
  • If you work indoors, take breaks every few hours and go outside. If possible, work in a well-lit environment (ideally from natural light).
  • During your lunch break, get outside for a good dose of UV-B sunlight. UV-B is needed for vitamin D synthesis and only hits the Earth’s surface around the middle of the day.

Decreasing light at night:

  • Replace all your LED and fluorescent light bulbs with incandescent bulbs. It may be more expensive to run, but think of the extra cost as an investment in your health. If you must use lights, use a RED LED night light. Better yet, simply use candles!
  • Within an hour of sunset, switch off all overhead lights, especially if they are newer LED or fluorescent lights. Instead, light candles (or you can use less than-optimal LED fake candles). Alternatively, use a low wattage incandescent Himalayan rock salt lamp. I use one at my apartment and it puts out a nice orange hue while releasing beneficial negative ions.
  • If you want to read in bed but don’t want to read by candle light, use a low wattage incandescent light bulb (15w or lower is best) in your bedside lamp. If you can get your hands on a RED lightbulb that would also help.
  • If you are serious about your health and sleep, restrict all artificial light sources 2 hours prior to sleep: no TV, no computer, no phones, and no eReaders. Buy books instead of eBooks. Print out articles to read at night. Talk with your partner over candlelit dinner. Listen to the radio. Play board games. Switch off. Relax
  • If you must use a screen in the hours leading up to bed, install f.lux. F.lux is software that changes the colour of your screen based on your time zone. As the sun goes down, the screen becomes tinted red as the blue frequencies are reduced. On your phone, try the Twilight app for Android. F.lux is available for iPhone but only on jailbroken devices. If you don't want to jailbreak, I recommend (and use) a blue blocking phone filter by Pavoscreen that reduces blue light emittance. I actually use this along with f.lux and I wear my bluelightblocking glasses! Another option is to invert the colours of your iPhone screen. If you’re watching TV, play around with the colour temperature and brightness settings to reduce blue light.
  • Wear Blue Blocker glasses. These are vital if you are going to be looking at screens late at night (even if f.lux is installed). Yes, they may look dorky, but there are some stylish Blue Blocker glasses coming out. They’re great for those times you have to use your phone right before bed. I wear them and so does my girlfriend. I can tell you, they help drastically!
  • Sleep in a pitch-black room. You shouldn’t be able to see your hand in front of your face. Cover any crack that leaks light with duct tape. Install black out curtains and put towels at the base of doors. The apartment I live in is right next door to a multi-level, 24-hour car parking lot. The only way we could eliminate the light leakage was by sticking tin foil across the windows and using black out curtains. Sleep is that important!
  • Turn off or cover any electronic devices that glow or put out light. Your room needs to be pitch black all night. Replace digital clocks with analogue clocks.
  • Wear an eye mask. Even though our skin senses light, our eyes are the primary sensors. Studies have shown that even a small amount of light perceived through closed eyelids can disrupt circadian rhythm and sleep quality.
  • If you must get up during the night, don’t turn on the main lights. If you really need light to go to the loo, look at having a low wattage incandescent lamp or a RED LED night light in the bathroom.

Closing Thoughts

Every time we move away from our natural environment, we disrupt our body’s cycles and therefore our health. Light has a massive impact on both of these things yet many are blind to its power, especially when it comes to sleep. Artificial light has changed dramatically over the past 150 years and more so over the past 10-15 years, with the popularity of white light energy efficient bulbs and screens. Today we are flooded with artificial blue light 24/7.

This 'new light' is not only disrupting natural hormone cycles, but it's causing leptin resistance, obesity, and health issues. Artificial light at night is making us fat.

Though the ideal solution would be living a ‘caveman’ lifestyle, this is impractical for most. Fortunately, there are solutions and workarounds that enable us to live in a modern, technology-based society without disrupting our circadian rhythm.

Cut screen time in the hours prior to bed, use candles for light after sundown, and wear blue-blocking glasses when you must use a screen.

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