May 26, 2021 3 min read

Written By: Dr. Allison Brager, Neuroscientist

Has your schedule ever been so consistent that you stopped needing an alarm clock to wake up?

Do you find yourself getting hungry at the same time every day?

This is not a coincidence.

This is purposeful, thanks to your body's 'circadian rhythm'.

So what is your "circadian rhythm"?

We'll dig into this below.

What is Your Circadian Rhythm?

At its core, circadian means “about a day”, with “circa” being the Latin root for “around” and “dia” is the Latin root for “day.”

"Rhythm" refers to the patterns of energy ebbs and flows throughout your day.

So why would our circadian rhythms need to be “about a day”?

It's because your body's internal circadian rhythm mimics the 24-hour cycle of a typical day.

When the sun is up, so are you.

When the sun is down and it's dark outside, you go to sleep.

Long before the invention of electricity, the circadian rhythms of humans solely relied on sunlight and nightfall to tell them when to hunt, when to eat, and when to sleep.

Our circadian rhythms still dictate when we “hunt,” eat, and sleep today, but the drive of circadian rhythms that lie in our body clocks are just not as pronounced as it was for ancient man. 


How Does Your Circadian Rhythm Work?

Years ago, three scientists received the Nobel Prize in Physiology and Medicine for discovering the body clock; they first discovered it in the fruit fly.

The body clock was later found to be present in all living beings (including us humans).

Nearly every organ and tissue of the human body has an internally ticking clock: the heart, the liver, the lung, the muscle, and of course, the brain.

The ‘master’ body clock lies deep in the brain and it coordinates with the other body clocks to determine what we do.

To no surprise, our body clocks control how much and how deeply we sleep.

Someone with a broken body clock due to an inherited genetic mutation, or after decades of shift work, often can’t fall asleep at a normal time or can’t get deep sleep.

The body clock is very important, it even determines the best time to exercise for your body.

How Does Your Circadian Rhythm Last?

The human body clock is slightly longer than 24 hours.

How do we know this?

In the 1930s, we learned of this from a long-term study of sleep that the grandfathers of sleep research—Drs. Eugene Aserinsky and Nathaniel Kleitman from the University of Chicago—conducted in Mammoth Cave, Kentucky.

Since then, this study has been replicated in labs across the world.

Why Is The Human Body Clock Longer Than 24 Hours?

 One advantage of a slightly slower body clock (relative to the Earth’s rotation) is that it gives us the flexibility to adjust our sleep schedules in a new environment.

This is especially important during times like the biannual daylight saving time change.

This is the reason why it is easier for most people to travel westward than eastward and why we find it easier to stay up late rather than to go to bed early.

How Can You Optimize Your Body Clock?

Optimizing your body clock will allow you to get deeper sleep at night and more energized days. Below are some tips for how to optimize your body clock.

1. Keep a Consistent Schedule.

The body clocks are “apprentices” to the “master” clock of the brain. The more stable our circadian rhythm is, the more stable our sleep is. A stable circadian rhythm helps us fall asleep easily, stay asleep, and wake up with little grogginess.


2. Expose Yourself to Morning Sunlight (with no shades).

Light is the most potent means for our brain and body clocks to “WAKE UP!” Light in the morning sends a very strong signal to the brain that we should be awake and helps to minimize afternoon slumps.

3. Eat Clean, Avoid Sugar.

There is growing evidence to show that high-fat, high-sugar foods interfere with the circadian rhythms in the brain and body. It happens in mice and it happens in humans.

If you must have a sugar fix, make sure to only eat sugar during the day when your body can afford a rise in blood glucose. Eating sugar at night causes blood glucose to rise too quickly, preventing us from getting our deepest sleep.

Do you have any sleep tips you follow? Leave them in the comments below!



Dr. Allison Brager is a neuroscientist specializing in the physiology and genetics of sleep and performance. Outside of work she enjoys Crossfit and other forms of fitness.



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