Jet lag is a mismatch between the body's internal clock and the local time zone, and it occurs when travelers rapidly cross multiple time zones. The condition can be prevented or reduced through strategic light exposure and gradual schedule adjustments before and during travel.

"If the circadian system is working correctly, you should have a problem with jet lag," said Charles Czeisler, professor of sleep medicine at Harvard Medical School. Jet lag is the body's normal response to skipping time zones, and certain groups—such as older adults, frequent fliers, and those with mood or sleep disorders—are more susceptible to its effects.

Light plays a central role in managing jet lag. "Light is the strongest signal that shifts the timing of the clock," said Helen Burgess, professor at the University of Michigan's Sleep and Circadian Research Laboratory. Exposure to light at the wrong time can push the internal clock in the wrong direction, prolonging symptoms. "Light before the crossover point will shift you later, and light after the crossover point will shift you earlier," Burgess said.

To minimize jet lag, travelers should seek appropriate light exposure by going outside, using light boxes, or wearing wearable light therapy devices. Conversely, avoiding inappropriate light—by napping, staying indoors, or wearing glasses that block blue light in the 460 to 480 nanometer range—can prevent the clock from shifting in the wrong direction.

Gradual schedule shifts before travel are also key. Adjusting sleep and wake times slowly toward the destination time zone helps prevent the body’s systems from being yanked apart all at once. "On average, we can only shift the clock earlier by about an hour and a half a day," Burgess said. Jet lag can thus be prevented by shifting the body clock before arrival.

Additional strategies include staying hydrated, avoiding alcohol, limiting caffeine—"maybe just one cup of coffee" at strategic times, Burgess said—and eating meals according to local time. Some travelers may also consult medical professionals about using melatonin.