WebMD has a good summary of what jet lag is and some of the soundest advice I've found on how to deal with it.
According to WebMD:
Jet lag is a temporary sleep disorder, but not temporary enough for many travelers. If you’re flying from San Francisco to Rome for a 10-day trip, for example, it may take six to nine days to fully recover. That’s because it can take up to a day for each time zone crossed for your body to adjust to the local time. If you’re traveling east to west, from Rome to San Francisco, jet lag could last four to five days -- about half the number of time zones crossed. Jet lag is generally worse when you “lose time” traveling west to east.
Here are their tips:
1. Simulate your new schedule before you leave.
“If you’re traveling east, start moving your bedtime earlier,” says Avelino Verceles, MD, assistant professor at the University of Maryland School of Medicine and director of the school’s sleep medicine fellowship. “Shift it a half-hour earlier each night for several nights before you leave.” If you’re traveling west, do the opposite. You can also try moving your mealtimes closer to the time you’ll be taking them at your destination.
2. Adapt to your new schedule while in flight.
Change your watch when you get on the plane. Try to sleep on the plane if it’s nighttime where you’re going or stay awake if it’s daytime -- but don’t force it. “It can be difficult to force yourself to sleep and that can cause frustration, which can then prevent sleep,” says Siebern. “If that happens, just try to rest as much as possible.”
3. Arrive early.
If you need to be on top of your game for an event at your destination, try to arrive a few days early, so your mind and body can adjust.
4. Stay hydrated.
Drink water before, during, and after your flight to counteract dehydration. Avoid alcohol or caffeine a few hours before you plan to sleep. Alcohol and caffeine can disrupt sleep and may cause dehydration.
5. Move around.
Get up and walk around periodically, do some static exercises, and stretch on the flight. But after you land, avoid heavy exercise near bedtime, as it can delay sleep.
6. Consider melatonin.
Melatonin naturally secreted in our bodies helps regulate our circadian rhythms so that we sleep at night. But the jury is still out on the effectiveness of the supplement melatonin to combat jet lag and aid sleep. Verceles suggests taking 3 milligrams of melatonin an hour or two before bedtime at your destination, and plan to sleep for 10 hours. Melatonin appears to be safe if taken short term, but its long-term effects are not known. If you want to try melatonin, check with your doctor first.
7. Try natural light therapy.
Exposure to sunlight helps regulate our circadian rhythms. ”On westward flights, get bright morning light at your new destination, and avoid afternoon and evening light exposure,” Verceles suggests. “On eastward flights, avoid early light exposure in morning and get as much light as possible in the afternoon and early evening. The light helps shift your body’s circadian clock, so that you feel rested and wake at appropriate times at your destination.”
8. Eat sensibly.
Some frequent fliers swear by jet lag diets -- such as eating a heavy diet for a few days before travel and fasting on flight day. No diets have been proven effective for preventing jet lag, however. “We do recommend not eating a high carb or fatty diet close to bedtime because that can be disruptive to sleep,” says Siebern.
9. Take a hot bath before bedtime.
A bath can ease sore muscles from travel and help you relax and wind down. The drop in your body temperature when you get out of a bath may also make you sleepy.
10. Minimize sleep distractions.
An eye mask or earplugs may help you sleep on the plane and at your destination. Try to eliminate distractions in your room at bedtime, such as light shining in through a window.
11. Consider medication.
It’s usually not necessary to get treatment for jet lag, but if these strategies don’t work for you, your doctor may prescribe or suggest medications to take temporarily to help you sleep or stay alert when necessary.