One of my best friends who I went to high school with was a HUGE anime/video game fan around the time when I was just beginning to explore outside of the Dragonball Z realm. He put me on to alot of anime and to this day I'm a huge anime fan. He fits the "overweight-can't get a girl" stereotype almost to a T. But at the end of the day he's a great person and a great friend.
What I think happens is that, like all forms of entertainment, some people use it as an extreme form of escapism. Think about the themes prevalent in a lot of mainstream anime. The meek hero,whom everybody doubts or dislikes in the beginning. Overcomes all odds and proves himself the "chosen one" by unlocking some special power that only he can harness while a harem of beautiful women with overly exaggerated bodily features fawn over him for 26-50 episodes.
A lot of young boys, whether we want to admit it or night, can relate in some way to the fantasy of being " special" or having some quality that allows us to perform some fantastic feat. Those young men who are unpopular, overweight, or awkward might cling to this fantasy because watching 26 episodes on a television screen is easier than getting up, working out, eating healthy, and developing the proper social skills to woo a woman.
There are actually a LOT of what you could consider "normal" anime fans, including me and my brothers and sisters. Anime has something for everyone.
