(UPI) – Intellectual work such as reading or writing induces a substantial increase in calorie intake, Canadian researchers suggest.

Dr. Angelo Tremblay of the University of Laval measured the spontaneous food intake of 14 students after each of three tasks: relaxing in a sitting position, reading and summarizing a text and completing a series of memory, attention and vigilance tests on the computer. After 45 minutes of doing each activity, participants were invited to eat as much as they wanted from a buffet.

The study, published in the Psychosomatic Medicine, found that despite the fact that the intellectual work required only 3 calories more than resting, the students spontaneously consumed 203 more calories after summarizing a text and 253 more calories after the computer tests -- a 23.6-percent and 29.4 -percent increase, respectively, compared to resting.

Tremblay said that blood samples taken before, during and after each session revealed that intellectual work causes much bigger fluctuations in glucose and insulin levels than rest periods.

The body could be reacting to these fluctuations by spurring food intake in order to restore its glucose balance -- the only fuel used by the brain, the researchers speculate.