While its largely a matter of personal taste and stereotypes don't hold, sometimes cultures can influence a person's preference. If you constantly see a certain body type, you get used to it and eventually the appeal grows.
But experience with relationships has just as much impact, if not more. After having a particularly nasty breakup with someone who had a definite physique, I could not stand to be around guys with the same build for a while.
These days the personality and mind, far outweigh a guy's build for me. But I have a friend in her 20's from Iwate that never misses a muscled body. It the first and foremost attraction for her. Recently we saw a guy whose facial features were ..... uh..... not easy on the eyes? But when the tshirt came off he had muscle definition that was truly impressive. She could not resist!
