Although it is a serious problem for airline personnel, most people can adjust to the new time zone although at first their sleep patterns will be seen to be abnormal based on their current time zone. It is recommended that a person changing time zones permanently should rest at least one day for each hour of change to allow their sleep/wake cycles to match local time with the fewest ill effects.
In addition to adjusting sleep patterns, jet lag can lead to difficulty concentrating, fatigue, headaches and irritability. Both appetite and the workings of the digestive tract can be problematic, with both constipation and diarrhea being common.
For frequent travelers, jet lag can combine with travel fatigue caused by dehydration and lack of usual routine.