One weekend in early May, I endured one of the most confusing experiences in my life: a two-legged, 24-hour flight across 13 time zones. I took off from Chicago on Saturday evening, and 24 hours later, I arrived in Bali on Monday morning. In that 24 hour period, I ate two dinners and two breakfasts, while lunchtime didn’t exist. I couldn’t tell when I was supposed to be hungry or go to sleep, so I ate when food was placed in front of me and I tried to sleep when I got tired.

I initially thought I had avoided this whole mess by sleeping through the first leg of my trip to my connection in Doha, Qatar. I had fallen asleep and woken up to see sunlight outside a distant window, thinking I had slept to a reasonable hour. I still felt exhausted though, so in a haze, I felt around for the right buttons to press on the screen in front of my face to check the time at our location. Far from my expectation, it was only 12:46 AM Chicago time, and we were just making our way across the southern tip of Greenland. If the time change wasn’t confusing enough, it turns out I was seeing daylight because we were flying over a region where the sun never completely sets at this time of year. I still had 18 hours and several thousands of miles to go.

Both of my flights were “overnight,” but I couldn’t sleep at all on my second flight. It was daytime in Chicago, and my body wanted me to get up and start my day. By the time I reached Bali, the sun was setting in Chicago, but it was just starting to rise where I was – and the sunlight combined with my excitement over reaching my final destination tricked my body once again into staying awake.

My body was confused. It did not know where or when it was. I felt like death.

How did my body fail me through this day and night-reversing journey? It all comes down to what John Arnold said in the novel Jurassic Park :

“Living systems are not like mechanical systems. Living systems are never in equilibrium. They’re inherently unstable. They may seem stable, but they’re not. Everything is moving and changing. In a sense, everything is on the edge of collapse.”

Arnold was talking about the instability and unpredictability of a tropical island filled with dinosaurs. And while part of my trip did involve visiting a tropical island populated by none other than Komodo dragons, the largest lizards in the world, it was my body that was on the edge of collapse during our flight to Indonesia.

For instance, I was hungry at the wrong times

When I’m at home, I tend to get by with a small bowl of cereal for breakfast, but by the end of the day, I have no trouble eating several pieces of deep dish pizza or a big bowl of spaghetti without breaking a sweat. It turns out that no matter when we wake up, when we eat our meals, or how big those meals are, we always get more hungry in the evening than in the morning. After we wake up in the morning, for example, we’ve been on a fast for about 12 hours, yet we don’t feel the urge to eat a big breakfast. (That’s not to say breakfast isn’t important.)

Think about this in reverse: Try fasting for 12 hours during the day. Skip lunch and see how you feel. Do you think you could make it to dinner without snacking, and then once you reach dinnertime, only eat a bowl of cereal to bring your energy back for another 4-5 hours before bed?

This might explain why, on my first evening in Bali, I only managed to eat half of my hamburger (a poor performance for me). It was breakfast time at home, and my body wasn’t looking for a big meal. Meanwhile, I woke up at 2am (lunchtime for my body) with hunger pains, and I downed half a bag of pretzel chips. Stupid body clock.

The time change was probably making me get fatter from my meals, too. This is because insulin, the hormone that lowers your blood sugar, might work harder during the day than at night. This makes sense if you think about it: we eat during the day. If I’m going to gorge myself with two slices of deep dish pizza for dinner, my insulin better stand at the ready!!

At night, when insulin stops trying as hard, more of the sugar we consume from our midnight snacks might get stuck in the body and get stored as fat.  Interestingly, when scientists studied this idea in mice and screwed up their body clocks, their insulin schedule got all screwed up, too, and they gained a lot of weight. Their insulin wasn’t processing all the sugar they consumed. Their insulin system seemed to enter a state of perpetual laziness.

Now think about what all of this could mean for a someone who has just flown to the other side of the world, where night is day and day is night. Not only did I wake up the next morning ready for dinner, but my pancake breakfast also made me fatter than if I had waited until dinnertime to eat the same thing.

My sleep schedule got all screwed up, too

Hunger is not the only factor that your body clock controls. The most well-known factor is sleep: Despite all the days you spent pulling all-nighters in college or sleeping in until 11 on weekends in your youth, your body has been and always will be on a roughly 24-hour sleep schedule, running incessantly to ensure that you receive the sleep you need. Like hunger, your need for sleep accumulates throughout the day until you can no longer stay awake. But while your brain cares about how much sleep you’ve been getting, that worry is nothing compared to the impact of environmental factors, including light.

Remember how I mentioned that I was wide awake when I reached the sun-drenched island of Bali, even though I had barely slept for 36 hours? Flying home from Bali, I had a similar experience. I left around midnight local time and, 24 hours later, when it had reached midnight again in Bali, I arrived at home in the early afternoon. I slept even less on the flight home than I did on the flight there, and it was the middle of the night in Bali when I got home, but somehow I still managed to stay awake for another eight hours or so and do all my laundry. I could only manage this great feat because the sun was out and my brain knew it was daytime (even if I didn’t want to admit it).

When the sun shines, and light enters your eyes, it’s fed into two places in the brain: 1) your visual centers, so you can see as well as control your eye movements and the amount of light your pupils let in, etc, and 2) the regions of your brain that control your body clock. When light hits those latter regions, it causes your brain to produce proteins that keep you awake. So when the sun is up, it can keep you awake, even if you’ve been on a plane for 24 hours and haven’t slept.

circadian rhythm body clock illinois science council By NoNameGYassineMrabetTalk✉ fixed by Addicted04 - The work was done with Inkscape by YassineMrabet. Informations were provided from "The Body Clock Guide to Better Health" by Michael Smolensky and Lynne Lamberg; Henry Holt and Company, Publishers (2000). Landscape was sampled from Open Clip Art Library (Ryan, Public domain). Vitruvian Man and the clock were sampled from Image:P human body.svg (GNU licence) and Image:Nuvola apps clock.png, respectively., CC BY-SA 3.0,

Hunger and sleep aren’t the only body functions a 24-hour rhythm.

What can I blame for my stupid body clock?

All of your body clocks (including for sleep, hunger, blood pressure, body temperature, and others) are handled in an itty-bitty region of your brain called the suprachiasmatic (soop-ruh-kye-asthmatic) nucleus (SCN). This region is called so because it sits above the optic chiasm, which is where the light coming from your two eyes comes together. If a rodent’s SCN gets damaged, it’ll still get the same amount of sleep as a healthy rodent, but it will sleep on an erratic schedule (like a newborn baby). People who have sleep disorders where they can’t sleep on a normal 24-hour schedule often have a problem with their suprachiasmatic nucleus.

Getting Over Jet lag

Your suprachiasmatic nucleus is there to keep you on a regular schedule, and it’s not equipped to handle a sudden shift in daylight hours, such as when you fly across the world.

Many people try to hack their brains to overcome jet lag as soon as possible. To trick their brains into realizing its daytime where they are, some people may put on a nightlight before they leave town and then use a sunlamp or some other bright light source during the day once they arrive at their destination.

A couple of years ago, researchers at Stanford found that people might more easily overcome their jet lag using a camera flash. Specifically, they found that flashing people with a really bright light while they were sleeping (even with their eyes closed) advanced their sleep schedule a couple hours…a pretty good head start on a timezone shift if you ask me. Maybe I’ll have my wife shine a camera flash on me the next time we take an overseas trip. Maybe I’ll feel a little less like death when I fly across the Atlantic. We shall see.


  • Ben Marcus

    Ben Marcus is a public relations specialist at CG Life and a co-editor-in-chief of Science Unsealed. He received his Ph.D. in neuroscience from the University of Chicago.

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