A team from Harvard and Beth Israel Deaconess Medical Center in Boston has concocted an elegant remedy to combat jet lag: the anti–jet lag fast. The international traveler, they counsel, can avoid jet lag by simply not eating for twelve to sixteen hours before breakfast time in the new time zone.
According to the Harvard team, the fast works because our bodies have, in addition to our circadian clock, a second clock that might be thought of as a food clock or, perhaps better, a master clock. When food is scarce, this master clock suspends the circadian clock and commands the body to sleep much less than normally. Only after the body starts eating again does the master clock switch the circadian clock back on.
The master clock probably evolved because when our prehistoric forebears were starving, they would have been tempted in their weakness to sleep rather than forage for the food they needed to survive. Today, when a traveler suspends his circadian clock before flying from Los Angeles to London, and then reactivates it upon breaking the fast, the clock doesn’t know that it should still be on Pacific Time. It knows only that the breakfast and the daylight declare morning in Mayfair, and it resets the body’s rhythms accordingly.