Adjusting meal times can help people beat jet lag on long haul flights, scientists say. Since our brain knows how to keep track of meal-times just as it does of daytime, the time at which one has the meals has a much bigger effect on the body clock than previously thought.

Researchers from Harvard University believe that avoiding food on long haul flights, then eating on arrival, could cut the time it takes to adjust to a new time zone. When our body is not given food, the "feeding clock" of our body overrides the light-based "time clock" keeping the person wake until they find food.

While the light-driven circadian rhythm is in charge most of the time, the mealtime clock takes over when body is deprived of food. By changing our behavior patterns and by not eating, shift workers and travellers can keep tiredness and jetlag at bay. The findings are reported in the journal Science.

According to researchers, a person should fast for about 16 hours to engage this new clock and avoid some of the uncomfortable feelings of jet lag. The altering of schedules also helps the travellers rev up this secondary clock and adjust more quickly to the new time zone.

Jetlag is a physiological condition which is a consequence of alterations to circadian rhythms; it is classified as one of the circadian rhythm sleep disorders. Such disturbances result from shift work, daylight saving time, chronic congenital disorders, or as the name implies, transmeridian travel as on a jet plane. They are known as desynchronosis, dysrhythmia, dyschrony, jet lag, or jet syndrome.

The condition is generally believed to be the result of disruption of the "light/dark" cycle that entrains the body's circadian rhythms.