What is a Circadian Rhythm, and can you live by it? | 9Lives
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Ever found yourself absolutely craving a mid-afternoon nap around 3pm? How about going to bed at what seems like a reasonable hour, and waking up exhausted? If you haven’t heard about the Circadian Rhythm, and how it affects nearly every aspect of your life, read on, as I try to understand what it is, and how to live by it.

What exactly is a Circadian Rhythm?

Also known as the “body clock”, your circadian rhythm is a biological 24-hour cycle that runs in the body. Occurring naturally, even when there is no light stimulus, this body clock manages your sleepiness, alertness, as well hormone release and repair processes. Interestingly, almost every organ in the body is run by an internal clock, like the liver and digestive tract.

Why the circadian rhythm is necessary

The main circadian clock is found in the hypothalamus of the brain, in a region known as the suprachiasmatic nucleus (I know, right? Try saying it five times fast). This is the region that is responsible for maintaining most of the functions of our body clock, and of special interest for this article, is the function thereof on hormone and metabolism regulation.

An important stress hormone known as Cortisol – yes, that one that makes you jumpy and agitated – is regulated by this clock. It peaks when you wake, promoting alertness and should gradually drop throughout the day. Obviously, in our busy and stressful everyday lives, this is not always possible. A hormone that works in an opposing manner is Melatonin. Where Cortisol promotes wakefulness, Melatonin promotes sleep.

A negative response has been established between insulin and melatonin. It has been found that Insulin actually inhibits the effectiveness and secretion of Melatonin, which is why you struggle to fall asleep after a big, late meal. So avoid those midnight snacks if you want to keep your circadian clock going!

Various studies have found that people and animals develop metabolic defects like diabetes, obesity, cardiovascular diseases develop in the absence of a functioning circadian clock.

So, with this in mind, I decided to live according to my circadian rhythm.

Intermittent Fasting vs Circadian Rhythm

Studies on the Circadian rhythm have found that, ideally, we should be eating within a 9 to 12 hour window. Sounds like intermittent fasting?

Intermittent fasting is another form of time restricted eating, but there are a couple of key differences. With intermittent fasting, for instance, black coffee and tea without sugar are allowed, as they have no calories. However, these things technically start your metabolism, even if you’re not consuming calories. Since it’s our metabolism that we’re focusing on, even black coffee and tea should be avoided if we want to keep the natural rhythm of our circadian clock.

Another difference is that people practicing intermittent fasting usually stick to a pretty strict eating window, such as the LeanGains method that dictates a fasting window of 16 hours fasting and eight hour eating window. Deciding to eat according to my circadian rhythm meant that I had more leeway, with an eating window of anywhere between 9 to 12 hours.

The way in which we consume carbohydrates is the third difference between these two types of restricted eating patterns. While the size and spacing of a carby meal Isn’t super regulated with intermittent fasting, it is when you’re eating according to your circadian rhythm. Our bodies are geared to be more insulin sensitive in the morning, and more insulin insensitive in the evenings. This means that our glucose control is best when we wake up, and worst just before we go to bed, so carb-heavy meals should be eaten for breakfast, when the glucose can be best utilised.


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Here’s the basic breakdown of the ideal day

Breakfast: At 8h00, I am only too happy to step out for my first cup of coffee of the day, along with a bowl of fiber- and carb-rich oats and some fruit to get my metabolism started on the right note. Over the last couple weeks I’ve developed a new love for frozen berries.

Lunch: Our office usually grabs lunch between 12h00 and 13h00 in the afternoon, and I try to use this time as an opportunity to get out and catch some rays. Mid-day slump is no joke, so the activity and bright sunshine helps me keep alert and stops me from reaching for something sugary. My lunch options usually have some good quality carbohydrates, fats and protein, and my go-to is a couscous and quinoa salad with lentils, cucumber, red onion and hummus.

Dinner: Trying to stick with the 10 – 12 hour eating period means that dinner should to be eaten by 8pm at the latest. I often make dinner by 7pm, giving me a nice 13 hour fasting period until the next morning’s breakfast. I try to make the last meals of the day lighter by incorporating some lean protein and lots of veggies.

Bed time: Having woken up before the sun has risen means that I am pretty ready to get into bed at about 21h30. The pre-bedtime habit of watching series is hard to break though, and it takes some serious getting used to. Luckily, I have a couple books calling my name and I try to swap words for moving pictures.

Was it worth it?

I’m not going to lie, it took some serious getting used to, from changing sleeping patterns, eating patterns, to forgoing that early morning caffeine boost and giving up my evenings binging on Pretty Little Liars (I know, don’t judge).

But it was worth it, despite the initial struggle. My sleep improved drastically, both due to the lack of bright light stimulus in the evenings, and the earlier mealtimes. Early mornings also became easier, especially towards the end of the month, since I was getting to bed on time and getting some good quality shut eye.

Dropping a little weight was also a happy side-effect, and not one that I had been expecting. According to research this could because of the fact that I was cutting down on my eating window and unknowingly eliminating calories that I would have otherwise been consuming late at night. The other possible reason is that I actually managed to improve my metabolism, effectively boosting it to burn more calories than I previously had. Personally, I believe more in the first reason. I don’t think I could have improved my metabolism that much in one month.

Physically, I also felt a lot better. I’m definitely not as sluggish during the day, I feel way more alert and, somehow, as I’m able to concentrate better.

I’m definitely keen to continue the journey; the effects and side-effects make it so worth while.

If you want to learn more about the (fascinating) science behind the circadian rhythm, check out mycircadianclock.org.


Just a girl, wishing she were a cat. You can find this peanut-butter enthusiast curled up in a sunny corner with a good book and a glass of wine.

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