How much energy does intensive mental activity burn?

Question

For example how much energy in kcal would I burn if I solved differential equations for one hour?

Or played chess?

Answer 1

In a 70 kg man (always the average man!) brain metabolism constitutes approximately 20% of the basal metabolic rate.
BMR is the energy expenditure to maintain body function at a complete rest which is ~7500 J per day for our average man. Mental activity can double the brain's energy consumption, so on average you will use 625 J during an hour's difficult calculus.

Answer 2

The brain is one of the major users of calories however a sleeping brain uses almost as much as an active one, so not a good way of losing weight..

Answer 3

The brain runs on about 10W which is about the same energy as a dim bulb