I had a friend who was a mezzo, a student in the Opera program at the New World School in Miami. She was definitely a bigger girl--a very Midwestern corn-fed/Scandanavian housefrau type (from MN, had eaten lutefisk regularly growing up, etc.). But man, her voice literally gave me the chills, it was so beautiful. However. She and her school friends I met were all fats. None of them to my knowledge ever went anywhere in opera; about ten years or so ago I looked up my old friend and I think I found her teaching music back in MN (couldn't find contact info to confirm). She took me to a dress rehearsal of Carmen at the school one day (dress rehearsals were open to the public, but less expensive than regular tickets. Still an amazing experience). I remember being very surprised that all of the main players were slim and attractive, and thinking, "Maybe this stuff matters in opera, too."