I've recognized the effects this has on my own brain, and you're absolutely right (for me, at least). And it makes me wonder about the origins of this particular chemical pattern, and how it came to be.

Perhaps it's some kind of evolutionary mechanism: back in the hunter/gatherer days, when food was scarce, those who had the particular genome to trigger the production of just the right set of chemicals for brain plasticity on an empty stomach were better able to form the neural pathways required for hunting and gathering food, thus able to survive.