Like football, swimming or tennis, chess is considered a sport. Although they sit for several hours straight, it has been measured that some chess players can burn several thousand calories a day, thanks to intense brain activity. And for good reason: just at rest, our brain consumes on average 20% of the body's total energy.
This energy is used to maintain the activity of vital organs, to allow us to breathe, digest and function normally. This translates into 350 to 450 calories naturally burned every day... for an adult, because in the case of a child aged 5-6 years, 'the brain can use up to 60% of body energy,' Doug Boyer, a researcher at Duke University in the United States, told LiveScience.
To take it a bit further: would it be possible to burn more calories by thinking a little harder? Scientists have tried to measure it and their answer is: yes... but there's a catch.
Thinking, a sport like any other?
'When you train to learn a new skill, the brain adapts to increase the transfer of energy to the brain regions activated by exercise,' says Claude Messier, a professor of psychology and neuroscience at the Canadian University of Ottawa. 'After a while, as we become more competent in a particular task, the brain no longer needs to carburise so much to accomplish that task and will no longer need so much energy.'
Besides, however intense your thinking may be, the loss of calories is not likely to be very high. To summarise, it is possible to burn more calories by thinking... but not enough to keep you in shape. There is nothing like a healthy diet and regular physical activity.