Factually speaking, when comparing the brain to your muscles, your muscles are incredibly energy efficient. The brain of a non-obese person makes up only 2% of their weight but accounts for 20% of the resting metabolic rate. Just by being alive the brain alone consumes more energy than the entire muscular system.
Robert Sapolsky, a neuroendocrinology researcher and human biological behaviour professor at Stanford's University, has found and suggests that chess players can burn up to 6000 kilocalories in a 12 hours chess tournament.
The average untrained person burns between 7 and 14 kilocalories a minute while running; trained athletes consume way less calories than that. So a chess tournament can and often burns more calories than a 12 hours marathon.
It seems to me that in terms of time efficiency, sitting on your ass studying and thinking is a favorable option when it comes to weight loss.
Are there any regimens and "brain" workouts for weight loss out there?