Attention late-night snackers: the food we devour right before bed is more likely to be stored as fat than food eaten during the day, new research suggests.
The study's findings fly in the face of conventional thinking that a calorie is a calorie, and it doesn't matter what time of day we take it in. This study, conducted on mice, suggests that when we eat is just as important as how much we eat.
Researchers from Northwestern University in Evanston, IL, studied two groups of lab mice; both groups were fed a high-fat diet containing the same number of calories and both had the same level of activity.
One group was fed at night -- the normal eating time for mice, since they're nocturnal -- and the other group was fed during the day.
After six weeks, the researchers found that the mice fed at their normal times, at night, saw a 20 per cent gain in their body weight. But the mice fed during their off-hours, during the daytime, saw a 48 per cent gain. The wrong-time-eaters also gained about eight per cent more body fat than the other mice.
While both groups of mice were allowed to eat as much as they liked and the daytime eaters took in slightly more calories, the difference wasn't enough to account for the wide disparity in weight gain, the researchers write in the journal Obesity.
The findings seem to show there really is a "wrong" time to eat, says study leader 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.
"How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out," he said in a statement.
The researchers suggest eating late at night, when our biology says we should be sleeping, disrupts our body's circadian system, or internal clock. Our circadian system governs not only our sleep cycles but our feeding and activity cycles as well.
Diane Arble, a doctoral student in Turek's lab who authored the report, says her team decided to conduct the experiment after noticing that shift workers 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," she said.
Night-time snacking has long been considered a no-no among dieters, since many tend to overeat at night, sometimes ingesting another's day worth of calories in one bowl of evening snacks.
But this research suggests that simply changing the timing of when we eat could make a difference.
"Better timing of meals, which would require a change in behavior, could be a critical element in slowing the ever-increasing incidence of obesity," Turek said.
