Washington: When you eat may be just as vital to your wellbeing as what you eat, says an Indian-American researcher.

Experiments in mice revealed that the daily waxing and waning of thousands of genes in the liver -- the body's metabolic clearing house -- is mostly controlled by food intake and not by the body's circadian clock as conventional wisdom believes.

"If feeding time determines the activity of a large number of genes completely independent of the circadian clock, when you eat and fast each day will have a huge impact on your metabolism," says Satchidananda (Satchin) Panda, assistant professor at the Salk Institute for Biological Studies.

The Salk researchers' findings could explain why shift workers are unusually prone to diabetes, high cholesterol levels and obesity.

"We believe that it is not shift work per se that wreaks havoc with the body's metabolism but changing shifts and weekends, when workers switch back to a regular day-night cycle," says Panda, who did his B.Sc from Orissa University of Agriculture and Technology, India.

In mammals, the circadian timing system is composed of a central circadian clock in the brain and subsidiary oscillators in most peripheral tissues.

The master clock in the brain is set by light and determines the overall diurnal (daytime) or nocturnal preference of an animal, including sleep-wake cycles and feeding behaviour.

The clocks themselves keep time through the fall and rise of gene activity on a roughly 24-hour schedule that anticipates environmental changes and adapts many of the body's physiological function to the appropriate time of day, says a Salk release.

"The liver oscillator in particular helps the organism to adapt to a daily pattern of food availability by temporally tuning the activity of thousands of genes regulating metabolism and physiology," says Panda.

"This regulation is very important, since the absence of a robust circadian clock predisposes the organism to various metabolic dysfunctions and diseases."

The study will be published in the Proceedings of the National Academy of Sciences. IANS