Interrupted sleep, irritability, disorientation, lack of motivation--these are only a few of jet lag's symptoms, and even the most seasoned travelers experience them to some degree when venturing across time zones.
Despite opinions to the contrary, the biggest cause of jet lag is not the number of hours traveled, but the time zones. Experts say that changing time zones throws off the body's circadian rhythms, which control the release of hormones and chemicals that let you know when to eat, sleep and wake up.
"Most processes within our bodies are regulated by a 24-hour timing mechanism or clock that can be called our 'biological clock,'" says Chris Colwell, a professor in psychiatry at the UCLA Medical School. "Rapid travel between time zones temporarily disrupts this biological clock and results in the set of symptoms known as jet lag." Because the body's clock can only adjust gradually, a little each day, adjusting to a new environment can be a slow process. "Our system does readjust but this takes time," Colwell says. "It can take a couple of weeks to adjust to the new time in Europe or Asia."
The direction of travel also plays a role in the severity of jet lag...