When you travel by plane between different time zones, your body clock gets left behind in the place where you started. It takes a few days to catch up with you in your new time zone. So, for a while, your body tries to act as if you're still in the time zone of the country you traveled from. You may feel wide awake at night and sleepy during the day.

 

 

 

 

 

Source:
Herxheimer A, Weaterhouse J.
The prevention and treatment of jet lag.
BMJ. 2003; 326: 296-297.

 

 

 

 

 

¹

Jet lag affects some people more than others, but in general the more time zones you cross, the worse it gets. For example, a flight from Los Angeles to London, England crosses eight time zones. This means the time in London is eight hours ahead of the time in Los Angeles. If you arrive in London at noon, your body thinks it's 4 a.m.

Jet lag seems to be worse flying east (from the United States to Europe, for example) than west (from Europe to the United States).

 

 

 

 

 

Source:
Herxheimer A, Petrie KJ.
Melatonin for the prevention and treatment of jet lag.
In: The Cochrane Library. Wiley, Chichester, UK.

 

 

 

 

 

² When you fly west, you gain extra hours in your day. This kind of jet lag might not be as bad because most people find it easier to stay up later than go to sleep earlier.

 

 

 

 

 

Source:
Herxheimer A, Petrie KJ.
Melatonin for the prevention and treatment of jet lag.
In: The Cochrane Library. Wiley, Chichester, UK.

 

 

 

 

 

²

Jet lag affects some people more than others. If you've had jet lag before, you're likely to get it again on future journeys.

Your body clock is driven by daylight and a chemical in your brain called melatonin. Melatonin tells you when to sleep. Your body starts to make melatonin when it gets dark outside, and stops when it gets light.

 

 

 

 

 

Source:
Herxheimer A, Weaterhouse J.
The prevention and treatment of jet lag.
BMJ. 2003; 326: 296-297.

 

 

 

 

 

¹

 

 

 

 

 

Source:
Arendt J.
Melatonin, circadian rhythms, and sleep.
New England Journal of Medicine. 2000; 343: 1114-1116.

 

 

 

 

 

³

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