Sleep

Aug 23, 2021

Circadian Rhythms and Improving Lifestyle

Understanding the significance of circadian rhythms can help you improve your lifestyle and health. We speak from personal experience.

If you’re reading this, chances are you believe in the importance of lifestyle for improving your health and wellbeing. Ever since life has thrived on Earth, all life forms have had to adjust to a predictable, daily change in light and darkness, in the form of sunrise and sunset, to regulate their bodily functions. So much so, that over time, these 24 hour rhythms have become essential for survival. Your body is no different. It follows internal 24 hour clocks that are benchmarked to the availability of light, also known as the circadian rhythms. [1] Understanding the working and significance of these cyclical patterns can help you optimize your lifestyle and position you for improved health outcomes. We speak from personal experience.

So, what are circadian rhythms?

Great question! Circadian rhythms are the different physical, mental and behavioral changes that take place in the human body on a daily basis according to its internal clocks. Almost every organ in the human body has its own clock. The brain is our master clock and determines when we sleep and wake up, mostly based on the exposure to light (darkness is a signal for the brain to start going to sleep). The clocks in the other organs (for eg: the stomach controlling digestion) are peripheral clocks that are influenced by the brain and other external factors, primarily the availability of food. These circadian rhythms together regulate the three foundations of human health - sleep, exercise and nutrition.

Before the industrial revolution, our human ancestors would sleep ~9 hours, get plenty of sunlight and exercise, and only eat 2-3 meals a day, as food was not that easily available, especially during the night. This ensured their circadian rhythms stayed in sync with the sun. However, in the 21st century, with artificial lighting, easy access to processed food and infrastructure development, we have started confusing our own biological clocks.

Most of us voluntarily override the natural light-dark cycle, by using electrical lighting to stay awake at night to watch Netflix, explore Instagram or to read books. This further triggers changes to our eating habits, with more and more opportunities for late-night snacking finding their way into our lives, sorely tempting our self-control. Research over the last few years has shown that prolonged deviations in circadian rhythms (staying up too late, not getting enough light in the morning) can cause or worsen conditions such as depression, irregular menstrual cycles, systemic inflammation, glucose intolerance, Type II diabetes and more. Per the famous researcher, Dr. Satchin Panda, there are at least 30 million people in the U.S., on average, that are affected by these diseases and more than 90% of healthcare costs go towards them. [2]

Source: Dr. Satchin Panda’s lecture on YouTube

Circadian Rhythms and Sleep

Circadian rhythms have a particularly important role to play in your sleep cycle.  All our hormones, brain chemicals and genes are programmed to rise and fall at predictable times. The human brain is wired to feel alert during sunlight and sleepy during the dark. Over-usage of bright lights at night, confuses the brain and disrupts its circadian rhythms. The amount of melatonin (sleep hormone) secreted is reduced and people face difficulty falling asleep or feel very tired upon waking up in the morning.

On a similar thread, we spend most of our daytime indoors, with no direct contact to sunlight. This goes against the very grain of our circadian rhythms, further exacerbating the misalignment and reducing our alertness as it is just not bright enough indoors to be able to reset our clocks. If this misalignment persists over weeks and years, we run the risk of developing mental health diseases such as migraines, depression, dementia, anxiety etc. Simply put, “lighting for vision is not the same as lighting for health”.

The general rules of thumb for sun exposure as outlined by Dr. Satchin Panda are given below:

  • For those who suffer from depression: Going outdoors for 15-60 minutes of sunlight (even in a shaded area) can be an effective anti-depression strategy.
  • For those who don’t suffer from depression: Even 30 mins of indirect sunlight (For eg: you can having breakfast near a window a day can be good enough for your circadian rhythms and sleep quality
  • Before going to bed, be sure to dim down your lights, at least 2-3 hours prior to going to bed. 

Circadian Rhythms and Nutrition

Feeding and fasting are very important phases in circadian rhythms. Feeding is when the body acquires food to convert into glucose and energy. Part of the glucose from food is stored to be utilized later, during the fasting period. It is during the fasting period, that the body draws upon its reserves of fat to conduct repair.

In the body’s natural circadian rhythm, digestion power and insulin sensitivity peak during the day as there exists the right enzymes and right microbiome for digestion. [3] At night, when you stop eating, your body starts repairing organs and goes into fat burning mode as there is not enough sugar in the blood. If food is presented at the wrong times and we continue to eat late at night every day or every other day, we run the very real risk of disrupting the entire cycle as the body will not have enough time to switch to burning fat and will not be able to repair the gut lining and our skin. It is as if our entire body will experience jet lag. 

In fact, many researchers recommend practicing “time-restricted eating”, i.e., slotting all your food consumption during one continuous, fixed time window each day. (8-12 hours a day) In contrast, a study with humans found that they typically eat for 15+ hours a day. For maximum benefit, doing early TRE (waking up early, eating first meal at ~8) is the best option. The benefits of time restricted eating include, less chances of consuming calories as the late night snacks tend to be the worst and getting deeper sleep at night. [4]

In fact, a study was conducted on a pair of mice, in which both mice got the same exact food with identical caloric intake. One mouse, however, had to eat it within a 8-12 hour interval (time restricted feeding), whereas the other mice could eat whenever. The mice following time-restricted eating: remained lean, whereas the other group of mice became obese. They then took the obese mouse and put him on time-restricted eating and the mouse went back to being lean. This was an extremely powerful finding because there is no drug that exists that could reverse obesity, diabetes etc. even in a mouse.

The general rules of thumb for nutrition as outlined by Dr. Satchin Panda are:

  • Avoid food for about ~1 hour after waking up
  • No coffee beyond 2pm 
  • Try a 10 hour eating window (8-12 hours), stop eating 2-3 hours before bed. 

Circadian Rhythm and Exercise

Lastly, your circadian rhythm also has an impact on exercise and your physical health. If your circadian rhythm is disrupted, you run the risk of lower muscle power and exercise endurance as was seen in a study conducted on mice. In fact, circadian rhythms are believed to be pivotal “in the balance of the beneficial effects or the detrimental risks of acute exercise.” [5] Getting enough bright light exposure prior to exercising (sunlight) could also help with loss in body fat, if that is one of your goals. [6] [7]

In conclusion, we would highly recommend building better habits around sleep and nutrition to shift your waking-sleeping cycle to earlier in the night. The benefits are too significant to ignore. 


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