Why do some vegetarians quit?

I'm sure it worked for you. I have a different experience, though. I'm a long distance rollerblader, and I found my performance & stamina increased dramatically (as well as muscle tone) after I cut all animal protein and began fasting regularly, once a week. Of course, I augmented my diet with tons of fruit & fruit juices ...something most vegetarians forget to do.
P.S. Mr. Universe 1971, Bill Pearl, was a vegetarian.

 

Very cool. I think you're right, it does vary quite a bit person to person. I know of some distance cyclists that are vegetarians and do well. Lots of alternative protein sources.