This Is Your Body on Jet Lag

You can’t avoid it, according to science. But you can make it less of a drag.

Nina Bahadur
Published in
4 min readSep 27, 2019


Illustration: Mark Wang

JJet lag is pretty much inevitable during long-distance travel. Wherever you go, whatever you do, you are at the mercy of your very powerful, very stubborn body clock.

“Our body clock has a strong effect on when we feel alert and when we feel sleepy across a 24-hour period,” says Leon Lack, PhD, a clinical psychologist at the Adelaide Institute for Sleep Health at Flinders University in South Australia.

Lack says the best way to understand jet lag is to think of a body clock as having a pendulum that swings back and forth between “feeling awake” and “feeling tired.” Most people feel awake when it’s light out and sleepy when it’s dark out, and they get used to falling asleep and waking up around the same time. But the pendulum swing can be interrupted when people are traveling, or if people keep inconsistent sleep schedules (like in the case of night shift workers).

“If you take that pendulum and fly it 10 time zones across the world, you’re faced with a different light and dark schedule, but your pendulum keeps going on your home time,” Lack says. “It starts producing sleepiness during an inappropriate time during the day in your current location. That oscillation between alertness and sleepiness, driven by our body clock, continues to take place.”

Global data indicates more people are traveling abroad than ever before, which means more jet lag. Earlier this year, the World Tourism Organization, a United Nations agency, reported that the number of people traveling overseas reached 1.4 billion in 2018, marking a 6% increase from the year prior. The group says it expects this figure to continue to grow.

If you’re one of the billions of people planning faraway travel, here’s what you should know.

“Exposure to bright light gently nudges the body clock so that our sleep period is pushed back into the nighttime.”

The symptoms, and how to lessen them

The main affliction of jet lag, as anyone who has ever experienced it can attest, is an intense desire to…