Scientists find midnight-snack center in brain.

Researchers have tracked down the location of a body clock that appears to be regulated by food.

Several studies have documented that many obese people eat more than half their daily calories at night. Some scientists have hypothesized that these people have an abnormal internal clock somewhere in their brains that tells them to eat at the wrong time.

Launching a search for that clock, Masashi Yanagisawa of the University of Texas Southwestern Medical Center in Dallas and his colleagues flip-flopped the feeding schedules of lab mice, which normally eat at night. The researchers fed the animals at a set time during the day for about a week and then didn't feed them for 2 days.

During the fasting period, the day-fed mice searched for food at their new feeding time. When Yanagisawa's team examined gene activity in these animals' brains, they found that genes in a region called the dorsomedial hypothalamic nucleus (DMH) cycled on and off rhythmically during the day.

Another set of mice had had continuous access to food and had eaten primarily at night. After a 2-day fast, their DMH gene activity was constant, the researchers report in the Aug. 8 Proceedings of the National Academy of Sciences.

These results suggest that abnormal DMH-gene activity might be responsible for nighttime eating in people, says Yanagisawa. If so, the finding would suggest new targets for antiobesity drugs.