With all the hormones and whatnot inside. Dopamine, adrenaline, melatonin, whatever. Also, there’s this Hunter S. Thompson bit on the… pineal gland?
If it had an effect on you, wouldn’t it be a really messed up high, all over the place? With uppers, downers etc mixed? (Not including the emotional implications of eating raw human brains.)
Why would you think it’s appropriate to comment if you’re just guessing? This is not a question where random guessing is appropriate.
Your reasoning is correct in that we do eat brains, and of course they don’t get us high.
You’re wrong is the fact that brain is mostly fat. That’s incredibly misleading. The brain is entirely nervous tissue plus supporting things like vessels. It does contain lots of myelin which serves to insulate axons, since nervous tissue is electrical. Myelin happens to contain a lot of fatty acids, but it is in no sense “fat”.