Food for thought: Intellectual activities make people eat more than when just resting, according to a study that sheds new light on brain food.

This finding might also help explain the obesity epidemic of an increasingly sedentary society in which people still have to think now and then.

The scientists had determined beforehand that the thinking sessions consumed only three calories more than resting. After the sessions, the participants were invited to eat as much as they pleased.

The students who had done the computer tests downed 253 more calories, or 29.4 percent more than the couch potatoes. Those who had summarized a text consumed 203 more calories than the resting group.

Blood samples taken before, during, and after revealed that intellectual work causes much bigger fluctuations in glucose levels than rest periods, perhaps owing to the stress of thinking.