And the subject of personality changing. I agree, I don't think it ever really does. BUT I believe you can condition yourself to, at the very least, temporarily mutate your personality. For example, all that hardcore training, I wasn't working at the time so all I did was train for like 3 hours a day, eat all day, and hang out with my girlfriend. I definitely maintained all my wit and mental sharpness, but I was MUCH more IN my body, so to speak. Oxygenated blood was literally being rerouted from my brain to my muscles, digestion, organs, etc.
You may not buy it, but I swear, if I'm doing like, heavy weight lifting (which I don't very often). The amount I have to eat, and all the recovery, I swear I'm dumber.