Symptoms:
Fatigue, lethargy, irritability, inability to sleep, trouble concentrating and making decisions, perhaps even diarrhea and a lack of appetite.

Cause:
Jetting across several time zones produces a sudden violation of your body's inner clocks. If, from America for example, you fly to Australia or Europe, you will experience jet lag—for you will suddenly be thrust into meals and wakefulness in the middle of "your night," and awake when your body tells you it is time for sleep.

Treatment:
Here are several suggestions, one or more of which may help:

• Get extra sleep beforehand. Drink plenty of fluids and be quiet and relaxed during the flight. Fly by day, arrive at night—and then soak up some extra rest. Get out in the sunshine the next day; this will help your body adapt. Obtain some exercise after arriving. Some people try living by their home clock—but most cannot do that.

• Try to avoid important decisions during the adjustment days. The general rule is that it will take one day of adjustment for each time zone crossed. So be prepared.

• When crossing only two or three time zones, it is known that going west is easier on the body than going east. This is because it is easier to get more sleep on arriving, since you experience more hours that particular day.