Being a vegan who completely neglects everything else logical and sane about nutrition.
I work with a guy who is a hard core vegan - as in no animals or animal products. Eggs, butter, dairy - all out.
This would by itself be foolish, but he compounds it by replacing meat with tons and tons of soy-derived products, eating hydrogenated oils like they were going out of style and of course, white breads like nobody's business.
If I were going to give advice about nutrition to a newbie, I would start, regardless of his goals by saying avoid processed grains, hydrogenated oils and soy.
This guy drives me insane!
So you know, we're both very lean, but I have about 40 pounds on him - muscle from my barbaric omnivorious quality.
Scary how some people can be infulenced to fanatacism, even at the cost of their own health.