The best way to beat jet lag on long haul flights is to avoid eating food while flying, according to researchers at Beth Israel Deaconess Medical Centre, Boston, Massachusetts.
The suggestion for international travellers comes from a study, which shows that the timing of meals has a much bigger effect on the body clock than previously thought.
Not eating food on long haul flights, then eating on arrival, could cut the time it takes to adjust to a new time zone.
Scientists have known for decades that meal times can affect the body clock, which has a natural period of about 24.2 hours. However, they have always thought that the key factor is light.
In investigating the intricacies of the body's biological rhythms, the research team - led by Patrick Fuller, PhD, HMS Instructor in Neurology - discovered the existence of a 'food-related clock', which can supersede the 'light-based' master clock that serves as the body's primary timekeeper.
The findings help explain how animals adapt their circadian rhythms in order to avoid starvation, and suggest that by adjusting eating schedules, humans too can better cope with changes in time zones and nighttime schedules that leave them feeling groggy and jet-lagged.
The suprachiasmatic nucleus (SCN), a group of cells in the brain's hypothalamus, serves as the body's primary biological clock.
The SCN receives signals about the light-dark cycle through the visual system, and passes that information along to another cell group in the hypothalamus known as the dorsomedial nucleus (DMH).
The DMH then organizes sleep-wake cycles, as well as cycles of activity, feeding and hormones.
"When food is readily available, this system works extremely well. Light signals from the retina help establish the animals' circadian rhythms to the standard day-night cycle," the study's senior author Clifford Saper, MD, PhD, Chairman of the Department of Neurology at BIDMC and James Jackson Putnam Professor of Neurology at Harvard Medical School.
However, if food is not available during the normal wake period, animals need to be able to adapt to food that is available when they are ordinarily asleep.
In order to survive, animals appear to have developed a secondary 'food-related' master clock.
"This new timepiece enables animals to switch their sleep and wake schedules in order to maximize their opportunity of finding food," Saper said.
"In addition to the oscillator cells in the SCN, there are other oscillator cells in the brain as well as in peripheral tissues like the stomach and liver that contribute to the development of animals' food-based circadian rhythms. Dissecting this large intertwined system posed a challenge," he added.
To overcome this challenge, the researchers used a genetically arrhythmic mouse in which one of the key genes for the biological clock, BMAL1, was disabled.
They next placed the gene for BMAL1 into a viral vector, which enabled them to restore a functional biological clock to only one spot in the brain at a time.
Through this step-by-step analysis, the researchers uncovered the feeding entrained clock in the DMH.
"We discovered that a single cycle of starvation followed by refeeding turns on the clock, so that it effectively overrides the suprachiasmatic nucleus and hijacks all of the circadian rhythms onto a new time zone that corresponds with food availability," says Saper.
He added that the implications for travellers and shift workers are promising.
"A period of fasting with no food at all for about 16 hours is enough to engage this new clock. 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," Saper said.
The study is published in the May 23 issue of the journal Science.