A North Western University study has found that eating at irregular times -- the equivalent of the middle of the night for humans, when the body wants to sleep -- influences weight gain.
The regulation of energy by the body's circadian rhythms may play an important role. The study is the first causal evidence linking meal timing and increased weight gain.
Fred Turek, professor of neurobiology and physiology in the Weinberg College of Arts and Sciences and director of the Center for Sleep and Circadian Biology says, "How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out.
We think some factors are under circadian control. Better timing of meals, which would require a change in behavior, could be a critical element in slowing the ever-increasing incidence of obesity."
The researchers found that simply modifying the time of feeding alone can greatly affect body weight.
Mice that were fed a high fat diet during normal sleeping hours gained significantly more weight (a 48 percent weight increase over their baseline) than mice eating the same type and amount of food during naturally wakeful hours (a 20 percent increase over their baseline). There was no statistical difference between the two groups regarding caloric intake or the amount of activity.
Over a period of six weeks, both groups of mice were allowed to eat as much high-fat diet as they wanted during their daily 12-hour feeding phase. (Much like many humans, mice have a preference for high-fat food.)
Since mice are nocturnal, the 12-hour feeding phase was during the day for those fed during normal sleeping hours and during the night for those fed during naturally wakeful hours. Food was not provided during the other 12 hours of their day.
Our circadian clock, or biological timing system, governs our daily cycles of feeding, activity and sleep, with respect to external dark and light cycles. Recent studies have found the body's internal clock also regulates energy use, suggesting the timing of meals may matter in the balance between caloric intake and expenditure.
North Western University
1.Deanna M. Arble, Joseph Bass, Aaron D. Laposky, Martha H. Vitaterna and Fred W. Turek. Circadian Timing of Food Intake Contributes to Weight Gain. Obesity, 2009; DOI: 10.1038/oby.2009.264