Shocks to your metabolism are a good thing but you can't let them be persistent.  

People who are jet-lagged,  work graveyard shifts and late-night snackers are engaging in activities that upset the body's "food clock," a collection of interacting genes and molecules known technically as the food-entrainable oscillator, which keeps the human body on a metabolic even keel.  That happens with binge eating during the holidays too.

A new study says the protein PKCγ is critical in resetting the food clock if our eating habits change. Normal laboratory mice given food only during their regular sleeping hours will adjust their food clock over time and begin to wake up from their slumber, and run around in anticipation of their new mealtime. But mice lacking the PKCγ gene are not able to respond to changes in their meal time. They sleep right through it.

In humans, this could help us understand the molecular basis of diabetes, obesity and other metabolic syndromes. A 'desynchronized food clock' may serve as part of a pathology underlying these disorders. More speculatively, it could even explain why night owls are more likely to be obese than morning larks.

"Understanding the molecular mechanism of how eating at the "wrong" time of the day desynchronizes the clocks in our body can facilitate the development of better treatments for disorders associated with night-eating syndrome, shift work and jet lag," says Louis Ptacek, MD, the John C. Coleman Distinguished Professor of Neurology at UC San Francisco and a Howard Hughes Medical Institute Investigator. 

Resetting the Food Clock

Biological clocks seem simple, just like a time clock on the wall, but inside they are complex also. Instead of cogs and flywheels, human biological clocks are composed of multiple interacting genes that turn on or off in an orchestrated way to keep time during the day.

In most organisms, biological clockworks are governed by a master biological clock, referred to as "circadian rhythm", an oscillator which keeps track of time and coordinates our biological processes with the rhythm of a 24-hour cycle of day and night. 

Life forms as diverse as humans, mice and mustard greens all possess such master clocks. And in the last decade or so, scientists have uncovered many of their inner workings, uncovering many of the genes whose cycles are tied to the clock and saying that in mammals it is controlled by a tiny spot in the brain known as the "superchiasmatic nucleus."

Scientists also know that in addition to the master clock, our bodies have other clocks operating in parallel throughout the day. One of these is the food clock, which is not tied to one specific spot in the brain but rather multiple sites throughout the body.

The food clock is there to help our bodies make the most of our nutritional intake. It controls genes that help in everything from the absorption of nutrients in our digestive tract to their dispersal through the bloodstream, and it is designed to anticipate our eating patterns. Even before we eat a meal, our bodies begin to turn on some of these genes and turn off others, preparing for the burst of sustenance – which is why we feel the pangs of hunger just as the lunch hour arrives.

Yet we know it can be reset rather easily - it just takes some discipline. A person who fasts and drinks only water, for example, will have hunger pangs disappear after a day, even though they should be far hungrier. The body becomes untrained rather quickly and scientist have known that the food clock can be reset if an organism changes its eating patterns, eating to excess or at odd times, since the timing of the food clock is pegged to feeding during the prime foraging and hunting hours in the day. But until now, very little was known about how the food clock works on a genetic level.

What Ptacek and his colleagues discovered is the molecular basis for this phenomenon: the PKCγ protein binds to another molecule called BMAL and stabilizes it, which shifts the clock in time.

How will that work on a practical level?  Culturally we knew it all along, that is why gym memberships spike upward in January, but exercise and a high-calorie diet mean twice as much work.  It's faster to eliminate all of the calories added during the holiday season and engage in more exercise also. There are no miracle diets or pills that will take the place of resetting your food clock.

 Published in the  Proceedings of the National Academy of Sciences.