Jet lag refers to a range of symptoms experienced while adapting to a different light-dark schedule following a flight to a new time zone.

It can affect people of all ages and is the result of your internal body clock not being able to adjust immediately to a new time zone.

Jet lag can disturb your sleep at night and make you feel drowsy and lethargic (lacking in energy) during the day. It can also sometimes cause digestion problems.

Crossing seven to 12 time zones usually results in more severe jet lag than crossing three to six time zones. Crossing one or two time zones doesn't usually cause any problems.

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