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Why the Brainy May Pack on the Pounds
According to a new study, doing intellectual work may actually prompt us to eat more than we would than after periods of leisure. These findings, published in the Journal of Psychosomatic Medicine, may help shed light on the current trend towards obesity in many countries.
In the study, 14 students completed 45 minutes of each of three tasks: resting in a seated position, summarizing a text that they had just read, and carrying out a set of memory and attention tasks on the computer. After each of these sessions, the students' voluntary calorie consumption was measured during a buffet-type meal.
After the task of reading and summarizing a text, the students ate on average about 203 more calories than they had after relaxing. Even more striking, after the memory and attention test, the students consumed a whopping 253 calories more than they had after relaxing.
So how many more calories did the students actually burn during the two brainy tasks? The researchers had already shown that each of the mental tasks only required about three more calories than relaxing.
Why, then, does this discrepancy occur? The researchers point out that glucose and insulin levels fluctuate much more during mental work than during periods of relaxation. It may be that the body is somehow attempting to reestablish a normal glucose level by increasing calorie intake in response to these fluctuations — particularly since glucose is the brain's sole source of energy.
The head author of the study, Jean-Philippe Chaput, points out that "[c]aloric overcompensation following intellectual work, combined with the fact that we are less physically active when doing intellectual tasks, could contribute to the obesity epidemic currently observed in industrialized countries." He adds that this mechanism "should not be ignored, considering that more and more people hold jobs of an intellectual nature."
The study took place at the Université Laval in Quebec, Canada.
October 10, 2008
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