Eat at the right time of day if you actually want to shed those extra pounds, for an American study so suggests.

Researchers at North-western University have found that eating at irregular times influences weight gain. They say that eating in the middle of the night, when the body wants to sleep, is not right because the regulation of energy by the body's circadian rhythms may play a significant role. "How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out," said Fred Turek, professor of neurobiology and physiology in the Weinberg College of Arts and Sciences and director of the Centre for Sleep and Circadian Biology.

"We think some factors are under circadian control. Better timing of meals, which would require a change in behaviour, could be a critical element in slowing the ever-increasing incidence of obesity," Turek added. During the study, the researchers observed that mice that were fed a high-fat diet during normal sleeping hours gained significantly more weight than those given the same type and amount of food during naturally wakeful hours. Referring to recent studies, the researchers said that the body's internal clock regulates energy use and that is why the timing of meals might be crucial to balancing caloric intake and expenditure.

They say that their findings may have implications for developing strategies to combat obesity in humans. "One of our research interests is shift workers, who tend to be overweight. Their schedules force them to eat at times that conflict with their natural body rhythms. This was one piece of evidence that got us thinking -- eating at the wrong time of day might be contributing to weight gain. So we started our investigation with this experiment," said lead author Deanna M. Arble, a doctoral student in Turek's lab.