The body's "feeding clock" may over-ride our natural sleep cycles
Adjusting meal times can help travellers recover from jet lag, a study suggests.
Harvard University researchers believe the brain has a second "feeding clock" which keeps track of meal-times, rather than daytime, after studying mice.
When food is scarce, the feeding clock overrides the master clock, keeping animals awake until they find food.
Thus, shift workers and travellers can keep tiredness at bay by not eating, they suggest in the journal Science.
Our daily sleep cycles, behaviour and metabolism are governed by a powerful master clock, which resides in an area of the brain known as the suprachiasmatic nucleus.
Disruption of these "circadian" rhythms have been shown to be linked with insomnia, depression, heart disease, cancer and neurodegenerative disorders.
This "circadian" clock is highly sensitive to daylight. But scientists have for several years been aware of a second "feeding" clock which is sensitive to our eating patterns.
To understand the relationship between the two clocks, a Harvard team studied mice which were missing a key clock gene, Bmal1.
By restoring this gene to different parts of the brain, one at a time, they were able to pinpoint the "feeding clock" to an area of the hypothalamus known as the dorsomedial nucleus.
What is more, by observing the mice's behaviour, they found that the "feeding clock" could supersede the circadian master clock, keeping the mice awake until they had the opportunity to eat.
Lead researcher Clifford Saper suggested travellers and shift workers may be able to use the feeding clock to adapt to changes in time zones and night-time schedules which leave them feeling groggy and jet-lagged.
"If, for example, you are travelling from the US to Japan, you are forced to adjust to an 11-hour time difference.
"Because the body's biological clock can only shift a small amount each day, it takes the average person about a week to adjust to the new time zone.
"And, by then, it's often time to turn around and come home.
"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."
Dr Neil Stanley, a sleep expert at Norwich University Hospital, said the discovery was "potentially very beneficial" to travellers and people who work unsociable hours.
"It's never going to make the symptoms disappear entirely, but it could certainly make them a lot more manageable," he said.