A study in the journal Psychosomatic Medicine looked at the food intake of 14 students after each of three 45-minute tasks - sitting down and relaxing; reading and summarising a text; and completing a series of memory, attention and vigilance tasks on a computer.
At the end of each 45-minute task, participants were allowed to eat as much as they wanted from a selection of buffet items.
The researchers found that students typically consumed 203 more calories after summarising a text, and 253 more calories after computer tests compared with the rest period.
This was despite the fact that the intellectual work only required three calories more than the rest period.
Study author Jean-Philippe Chaput commented: "Caloric 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 industrialised countries.
"This is a factor that should not be ignored, considering that more and more people hold jobs of an intellectual nature."
The researchers found evidence that the stress of intellectual work may cause fluctuations in blood glucose and insulin levels.