Scientists are studying a wide range of strategies to help long-distance travelers avoid the dreaded feelings of jet lag.

Frequent fliers often have sworn-by practices to combat jet lag, whether it's adjusting a sleep schedule days before a trip, taking the hormone melatonin, seeking out bright light at certain times, or forcing the body to eat and sleep on local time immediately upon arrival.

What works best? The news from most researchers appears to be that the best formula is a combination of all of these tactics.

As a general rule, it takes about a day for each time zone traveled for a person's body clock to catch up to the local time, researchers say. The severity of jet lag varies widely. Traveling east, to a later time zone, seems to be much harder than traveling west. Crossing more time zones makes it more difficult to avoid symptoms, which include sleepiness and confusion. Older people and very young people fare worse with jet lag, probably because older people's body clocks are deteriorating and very young people's body clocks are still developing, researchers believe.

Helen Burgess, director of the biological rhythms research lab at Rush University Medical Center, developed a plan for herself to avoid jet lag during a trip to Egypt, eight time zones away from her home in Chicago. For several days before the trip, Dr. Burgess advanced her bedtime by one hour each night, and got up an hour earlier each morning. She took a low dose of melatonin in the early afternoon to help her reset her body clock. And she sought out bright light in the very early morning, avoiding wearing sunglasses to maximize her exposure, to wake up her body clock.

In Egypt, Dr. Burgess says she had just one morning when it was hard to get up. 'Without the preflight shift [in schedule] I could have had jet lag for over a week, pretty much the duration of the trip,' she says.

While most researchers agree that light exposure and melatonin can help reduce the symptoms of jet lag after arriving at your destination, not everyone thinks it makes sense to switch sleep schedules before a trip, which can cut into social time with family and friends. 'I don't see the point of giving yourself jet lag before you leave,' says Alfred J. Lewy, director of the sleep and mood disorders lab and senior vice chairman of the department of psychiatry at Oregon Health & Science University.

Some of the new thinking about jet lag is coming from work with animals. Gene Block, a professor of psychiatry and biobehavioral sciences at University of California, Los Angeles, and colleagues found that by middle age, the signal the master body clock in the brain sends out to other internal clocks to help resynchronize the different processes gets weaker. As a result, it took longer in experiments for older mice to adjust to time changes than younger mice. Researchers often chose time-zone shifts of six hours in their studies.

Some of the research in mice indicates that the master clock typically adjusts to a new time zone after around three days. However, some other internal clocks readjusted at different rates and weren't all workingcorrectly until the eighth day.

Dr. Block, who is 64 years old, says he has noticed that his jet lag lasts longer as he has aged. On a recent trip to Doha, he says he ate his meals on local time even when he wasn't hungry to try help his liver get synchronized more quickly to the local clock.

Most people have body clocks that run longer than 24 hours, which generally makes it easier to fly west than east, researchers say. When people fly west, they have to stay up later before going to bed. That is easier to do than having to go to bed earlier than normal.

Seeking out day light at certain times, and avoiding bright light at other times, are some of the main strategies researchers recommend for resetting the body clock faster. Daylight is one of the key clues the master clock in the brain receives from the retina that it needs to resynchronize. In general, travelers going east are advised to seek out afternoon light, and travelers heading west should seek out morning light. If the climate or hour of the day at the new destination don't allow for lots of light, a small, portable light box, some of which double as an alarm clock, can be purchased.

Avoiding light at certain hours also is important to help the body clock reset. Traveling east, it is generally advised to avoid morning light; going west, avoid afternoon light. But researchers say these recommendations need to be tailored to each individual, depending on whether you are normally an early riser, and what the local time is when you arrive.

Melatonin is another popular way to help shift the body clock faster to a different time zone. Dr. Lewy, of Oregon Health & Science, recommends taking a small dose at the local bedtime every evening until the body clock resets. When traveling west, he recommends taking melatonin during the second half of the night. Although it is sold over-the-counter, melatonin isn't approved by the Food and Drug Administration and researchers disagree on the optimal dose. A doctor should be consulted before taking it.

Some people have shifted their body clocks but not everyone has the discipline or interest in such regimens to ease jet lag. Most travelers arrive in a new time zone, take a sleeping pill to fall asleep at bedtime, drink coffee during the day to stay awake, and wait it out until they feel better, says Charmane Eastman, a professor of behavioral sciences at Rush University Medical Center in Chicago, who has devised strategies for people seeking to minimize jet lag. 'You have to be motivated to want to do something about it,' she says.

For short trips, readjusting the body's clock might not seem worth the effort. Jim Waterhouse, a professor of biological rhythms at Liverpool John Moores University in Liverpool, England, says he often recommends that people crossing three time zones or less and only staying three days or less might want to consider maintaining the same sleeping and waking schedule from home rather than trying to shift the body clock. 'Keep your watch set to the time at home and act accordingly,' he says.