Does Thinking Make Us Fatter?

That's true not only in the world of employment, but in the world of entertainment as well. Many people are spending more time playing computer games, some of which can be intellectually challenging, than playing tennis, for example.

The researchers are members of the university's department of medicine, and they specialize in kinesiology, the mechanics and anatomy of human movement. The 14 women in the study were all students, ranging in age from 20 to 30 years. All were in good health, with no eating disorders, normal weight, and free of food allergies.

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During a two-month period they were each required to participate in three 45-minute exercises consisting of relaxing in a chair, reading a document and writing a summary of 350 words, and "a cognitive task consisting of a comprehensive battery of computerized tests."

Each participant was tested separately from the others.

Each "came into the lab at 8 a.m., and we gave each participant a standardized breakfast," Chaput said. "After that we started the exercise at 10:30 a.m., one participant at a time, and they came every two weeks. At about 11:30 a.m. we gave them a buffet type of meal, comprising a lot of food."

The food in the buffet was weighed and analyzed before and after the lunch, so researchers knew precisely how much and which type of food each participant had eaten. Various tests during each exercise also told the researchers precisely how many calories the participants were burning at the time.

The participants burned only about three calories more during each of the two "knowledge-based" experiments than during the 45 minutes when they rested in a comfortable chair. So the caloric expenditures were relatively quite low for mental tasks compared to the period spent relaxing.

But the intake was significantly higher. Participants consumed 203 more calories after the reading experiment, and 253 more calories after the computer tests, than the resting participants. That's an increase of 23.6 percent and 29.4 percent, respectively.