Skipping airplane meals and fasting for an extended period of time may help ease travellers' jet lag, suggests a U.S. study on circadian rhythms.

Lead researcher Patrick M. Fuller of the Beth Deaconess Medical Center in Boston theorizes a food-based clock overrides the standard light-based regulator in animals when food is scarce.

"When food is plentiful, circadian rhythms of animals are powerfully entrained by the light-dark cycle," said the study published in the May 22 issue of Science.

"However, if animals have access to food only during their normal sleep cycle, they will shift most of their circadian rhythms to match the food availability."

Researchers studied the interplay between the light-driven and food-based clocks in genetically altered mice.

"For a small mammal, finding food on a daily basis is a critical mission. Even a few days of starvation, a common threat in natural environments, may result in death," the study said.

"Hence, it is adaptive for animals to have a secondary "master clock" that can allow the animal to switch its behavioral patterns rapidly after a period of starvation to maximize the opportunity of finding food sources at the same time on following days."

The shift is a survival mechanism in small mammals that forces them to change their sleeping patterns, Fuller suggests. One starvation cycle is enough to override the traditional light-based circadian clock, the study suggests.

"This new timepiece enables animals to switch their sleep and wake schedules in order to maximize their opportunity of finding food," said researcher Clifford Saper in a release. Saper said the findings could prove relevant to shift workers and travellers.

"A period of fasting with no food at all for about 16 hours is enough to engage this new clock," says Saper. "So, in this case, simply avoiding any food on the plane, and then eating as soon as you land, should help you to adjust — and avoid some of the uncomfortable feelings of jet lag."