I just completed my 21st half marathon in 5 years last month. I am 175 lbs and 5'4". I was over 200 when I started running. Two+ years ago I did a 30 day vegan diet which turned into a year. I am now on what i would call a low meat, low dairy diet. I cook vegan at home but about once a month I will indulge in a burger or some other meat at a restaurant. Even though I am not eating vegan now my diet has changed so much in the past 2+ years. We eat beans and pasta and stir frys with nuts and hearty salads with avocado and olives. Running and eating vegan have not been an issue at all. I feel lighter and I have less achiness after I run when I don't indulge in meat or dairy. I did a 30 day raw diet (and lost 12 lbs) last March and that was a little more challenging with running. I would bring raw almonds and raisins on long runs (I was training for a marathon during that time and actually ran a 1/2 marathon while raw). So running vegan seems so easy compared to that. Oatmeal and bananas are great breakfast foods before you run. Dried fruit and nuts are good run fuel (although you can eat the regular energy gels and blocks etc. as they are vegan).
It is funny to me because so many athletes think you "need" animal protein to perform, particularly for endurance events and my diet is questioned frequently "Where do you get your protein? Where do you get your calcium?" I explain that calcium is in leafy greens and broccoli and it is better absorbed by the body than dairy and I get protein in all the whole foods I eat, but specifically nuts, seeds and legumes. But when I am not eating vegan or raw and I swing into Starbucks with other runners to get my post run soy latte and a (non-vegan) donut my friends don't even think to ask me where I am getting my calcium and protein!!
I am happy to correspond if you want to PM me about running vegan. I am starting an 8 week detox (that is why I joined the forums, for support) on 1/1 so I will be eating vegan with no sugar, caffeine, coffee, refined carbs, alcohol (and no meat or dairy). I am hoping to drop some weight as I just started training for another marathon (hoping to PR) and I will be doing a half ironman triathlon in August and then Ironman in 2011 so it is a priority for me to drop at least 20 lbs this year.