So apparently, a brain daydreaming or one fully immersed in a complex activity don't exhibit that much difference in energy usage, only consuming around 100 calories extra a day for mentally challenging activities.
Heck yeah it do. The brain is powered by glucose, and more brain activity will use much more of it. Jokingly, it's how I can tell a new engineer from one that is extremely experienced: A bright young engineer is usually skinny from problem solving all day. An older one is likely stuck in more meetings where brainpower is a liability and is probably on the heavier side.
Also, as an occasional eater of magic mushrooms, I keep packs of glucose in the house that are typically used for diabetic emergencies. Psilocybin pushes a brain into overdrive and causes my blood sugar to nosedive. (There are studies about possibly using psilocybin as a diabetic treatment to improve pancreatic function, btw..)