Study: Days are for eating; night for sleep

Yet another study suggests humans are meant to eat at certain times of day, emphasis on day.

Studies on the human circadian clock show our bodies have natural tendencies for when we should eat, sleep and be active. The eating and activity seem to blend well with daylight, when certain hormones and other body chemicals are released that promote eating and activity. At night, hormones shift to encourage sleep.

A study of mice shows the consequences of mixing up that pattern. Researchers at Northwestern University found that mice fed a high-fat diet during normal sleeping hours gained 48 percent more weight than mice eating the same type and amount of food during their naturally wakeful hours. Those mice gained 20 percent beyond their weight at the start of the study.

"How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out," said Fred Turek, the lead author of the study.

The study was published online in the journal Obesity.