Health & Wellness

What is jet lag and how does it affect your sleep?

Don’t let this common complaint spoil your trip! Read on to find out what causes jet lag and how to reduce the symptoms.
Published March 16, 2021

Ah, the anticipation of a big trip: the sights you’ll see, the meals you’ll enjoy, the weird fatigue and crankiness you’ll battle for the first two days you’re there. If that last part sounds unpleasantly familiar, you’re no stranger to jet lag. Nearly every traveler experiences it at some point, according to the American Sleep Association. While you may not be able to sidestep the condition completely, some simple measures may help you cope.

Read on for the lowdown on what causes jet lag, as well as expert tips for dealing with it—so your getaway doesn’t feel like a grind.

What is jet lag?

Jet lag, also known as desynchronosis, is a temporary condition that occurs when your body’s internal clock is out of sync with the actual time in your surroundings. Anytime you travel to a new time zone—whatever your mode of transportation—your body needs to play catch-up and acclimate to the new schedule. That mismatch in the meantime is the crux of jet lag, says sleep specialist W. Chris Winter, MD, author of The Sleep Solution. Jet lag commonly causes sleep issues, as well as other bothersome symptoms.

What causes jet lag?

Each of us has an internal body clock controlled by circadian rhythm, a cycle of about 24 hours that tells the body when it’s time to feel sleepy or stay awake, among other important functions. The cycle is largely influenced by light exposure, plus factors such as body temperature and activity level. When your circadian rhythm isn’t in sync with your surrounding time zone, it causes sleep disruptions that trigger jet lag symptoms (more on those in a sec).

Jet lag is generally more likely to occur when you travel across multiple time zones, says American Academy of Sleep Medicine spokesperson Raj Dasgupta, MD, an assistant professor of clinical medicine at the Keck School of Medicine at the University of Southern California. It also tends to hit harder when you travel east.

Symptoms of jet lag

On the first morning at your new destination, your travel buddy practically leaps out of bed and sprints to the breakfast buffet, while you feel moody and meh. What gives? Jet lag symptoms—and their severity—depend on the individual person, Dr. Dasgupta says. The most common effects of jet lag include:

  • Insomnia: No surprise here! When your circadian rhythm is aligned with a different time zone, you may have a tough time falling or staying asleep.
  • Daytime sleepiness: When your normal bedtime is earlier than the local time, your body may start winding down during the day. Pile on insomnia, and your fatigue may be even worse.
  • Change in mood: You probably know from experience that tiredness can trigger crankiness, but jet lag may enhance the grouch effect: Research shows that disruptions to circadian rhythm are linked to a greater likelihood of experiencing irritability, mood swings, and anxiety.
  • Difficulty concentrating: You might want to refrain from scheduling a morning meeting after a redeye flight: Jet lag can take a temporary toll on attention and memory that could make your conference-room gathering a tough slog, Dr. Winter says.
  • Digestive upset: Circadian rhythm doesn’t only control sleep; it helps signal mealtimes, too. “When you travel, you eat at times when your body isn’t expecting food,” Dr. Winter says. Stomach issues such as diarrhea or constipation often come with the territory.

How long does jet lag last?

Ask five travelers this question and you’ll likely get five different answers. “Some people adapt more quickly, while others hang onto symptoms longer,” Dr. Winter says. “On average, it takes about a day for each time zone.” So if you hop a three-time-zone flight from Los Angeles to New York City, it’s reasonable to hope that any resulting jet lag will subside within three days. Crunch the numbers for your own trip and try to plan for flexibility when you arrive in case you feel zonked for a bit.

Can jet lag affect your weight?

There’s no evidence to show that jet lag directly affects body weight. To the extent that it causes sleep deprivation, though, jet lag may ramp up appetite and cravings in some people, which could conceivably influence a person’s food choices, suggests a study published in The Journal of Clinical Endocrinology & Metabolism. Other people may experience a decrease in appetite with jet lag, according to a research review published in the Lancet. Consider creating a travel-friendly healthy-eating plan for support in sticking with your goals.

Is there a cure for jet lag?

Unfortunately, there’s no instant fix for jet lag, but you may be able to ease the symptoms with measures that encourage your body to adjust, Dr. Winter says. It’s all about giving your circadian rhythm a nudge in the right direction.

How to beat jet lag

What you do before you leave, while you’re en route, and when you arrive may help you sidestep severe jet lag and shake off the symptoms more quickly. Consider this your long-haul game plan:

  1. Shift your schedule in advance: If you know ahead of time that you’ll be taking a big trip, start adjusting your schedule a few days before you go. Gradually shift the times you go to bed and wake up to be closer to your destination’s time zone, Dr. Winter says. For example, if you’re traveling west, stay up later and try to wake up later so the time shift is less of a jolt once you arrive.
  2. Up your water intake: Dehydration can exacerbate jet-lag symptoms by causing fatigue and sleep disruptions unto itself, Dr. Dasgupta says. His suggestion for staying hydrated: Keep a water bottle handy throughout your travels and sip regularly throughout the day. If you're in the market for a new reusable option, this WW Canteen Style Water Bottle will keep your drink cold without taking up too much space in your carry-on. And did you know? You can track your water intake right in the WW app to ensure you’re hitting a healthy target for you.
  3. Limit alcohol and caffeine: Caffeinated drinks can have a stimulant effect that interferes with sleep. And while a couple of glasses of wine might make you feel drowsy in the moment, alcohol can ultimately disrupt sleep cycles and reduce the quality and quantity of your slumber later on, Dr. Winter says. While everyone’s tolerance varies, you might enjoy easier sleep—and a quicker recovery from jet lag—if you keep coffee and cocktails to a minimum in the 6 or so hours leading up to bedtime.
  4. Live on local time: As soon as you board the plane, adjust your watch and personal devices to display the time at your destination. When you arrive, eat according to local mealtimes, and try to carry out your usual sleep routine in accordance with the clocks around you. If your hotel bed is calling you midday, try to limit yourself to just a quick nap. “Set an alarm for 20 minutes so you don’t go into a deeper sleep,” Dr. Dasgupta advises.
  5. Get moving outside: Landing during daylight hours? Head outdoors and explore, if you have the chance. The combo of sunshine and movement may help tell your body it’s go time, not bedtime: Light plays a big role in regulating your circadian rhythm, Dr. Winter says, and even a short bout of exercise boosts energy, according to a University of Georgia study.

The upshot: How does jet lag affect your sleep?

Jet lag is a common and normal response to zipping across time zones. Though temporary, it can seriously affect how you feel. When your inner clock isn’t in sync with the time in your surroundings, you may experience insomnia, daytime grogginess, as well as changes in appetite and mood. While there’s no surefire cure for jet lag (apart from, y’know, never traveling), some simple steps may help minimize symptoms and help you bounce back more quickly.


Sharon Liao is a freelance writer and editor specializing in health, nutrition, and fitness. She lives in Redondo Beach, California.


This article was reviewed for accuracy in July 2021 by Stephanie L. Fitzpatrick, PhD, senior manager for multicultural programs at WW. The WW Science Team is a dedicated group of experts who ensure all our solutions are rooted in the best possible research.

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