Has your schedule 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 and you can thank circadian rhythms.

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

So why would our circadian rhythms need to be “about a day”? It is because it takes the Earth 24 hours to complete a full rotation leaving us with 24 hours in a day. Yes, it’s that simple.

Long before Netflix, smart phones, and even the greatest and worst invention of mankind, electricity, the circadian rhythms of humans and all animals on this planet solely relied on the rotation of the Earth 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 Internal Body Clock Work?

Earlier this year, three scientists received the Nobel Prize in Physiology and Medicine for discovering the body clock; they first discovered in the fruit fly. The body clock was later characterized across the animal kingdom, including humans, and in all tissues of the body.

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, the body clocks hugely control how much and how deeply we sleep.

Someone with a broken body clock brought on by an inherited genetic mutation (such as advanced phase sleep disorder, ASPS) or after decades of shift work (shift work disorder, SWD) can’t fall asleep at a normal time or can’t get deep sleep.

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


How Long Is The Human Body Clock?

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 flexibility to adjust our sleep schedules in a new environment. 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?

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 help us fall asleep easily, stay asleep, and wake up with little grogginess.


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.


Eat clean, avoid sugar.

There is growing evidence to show that high-fat, high-sugar foods break down our 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.


Dr. Allison Brager is a neuroscientist specializing in the physiology and genetics of sleep and performance. She is author of Meathead: Unraveling the Athletic Brain, which debunks the myth of the "dumb jock" and serves as a manual for optimizing athletic performance through neuroscience.