Jet lag can be prevented by "hacking" into the body's circadian rhythm during sleep using a flashing alarm clock, Stanford University has discovered.
Many people suffer from the sluggish feeling after flying to a different time zone as the body struggles to re-orientate itself.
But scientists have shown it's possible for travellers to get a head start on jet lag before it happens by tricking the body into thinking that dawn is breaking earlier.
Being subjected to short flashes of light while asleep before a trip speeds up the process of adjusting to a different time-zone, researchers have proven.
"This may be a new way of adjusting much more quickly to time changes than other methods in use today," said Dr Jamie Zeitzer, assistant professor of psychiatry and behavioural sciences at Stanford University in California.
Dr Zeitzer said it was a kind of "biological hacking" that convinced the brain the day had started earlier.
Researchers recruited 39 participants aged 19 to 36 and synchronised their sleep routine so they were going to bed and waking up at the same time every day for about two weeks.
They then had the volunteers sleep in the lab, where half were exposed to a sequence of flashes of various frequencies for an hour while asleep.
The study found that a sequence of two-millisecond flashes of light, similar to a camera flash, 10 seconds apart elicited a nearly two-hour difference in the onset of sleepiness the following day. The therapy effectively creates a "false dawn" in the brain, which more closely synchronises with sunrise in a new country, if travelling from West to East.
Dr Zeitzer said: "If you are flying to New York tomorrow [and] normally wake up at 8am, you set the flashing light to go off at 5am. When you get to New York, your biological system is already in the process of shifting to East Coast time."
The researchers, who published their work in the Journal of Clinical Investigation, said the concept could also help shiftworkers adjust to odd work patterns.