The natural circadian clock located in the hypothalamus of the brain provides signals to the body on when to wake up, eat, and sleep based on responses to light. According to a recent study from Harvard University published in Science, there is a second circadian clock that kicks in when food is withheld during the normal wake cycle. The authors of the study suggest that manipulation of this food-related circadian clock might help in preventing jet lag.

Previous studies in animals have shown that, if mice are fed only during the times of the day when they would normally be sleeping, they can alter their normal circadian block to match the availability of food. In order to better understand how mice are able to shift their circadian rhythms, the scientists in this study examined a group of mice that lack the gene, which usually regulates the body's circadian clock. They then delivered the missing gene into different parts of the mouse brain to study the effects. They found that if they put the gene into a region of the hypothalamus called the suprachiasmatic nucleus, the mice were able to adjust their waking and sleeping schedules in response to light, but were not able to adjust their eating schedules. However, if they put the gene into a region called the dorsomedial nucleus, the mice were able to adjust their eating schedules, but not their sleep-wake cycle.

According to the authors of the study, approximately 16 hours of fasting is enough to trigger this food-related circadian clock in the dorsomedial nucleus and help to prevent jet lag when traveling between time zones. So far, there are no corroborating studies in humans, but it might be worth a try.