Not vegan but a vegetarian.
I am not against eating meat per say but I do object to the manner that we in the west gorge ourselves on factory reared meat. If it was a case of fattening up a pig to slaughter and eat just once a year, I could go along with the omnivore argument. However, I challenge anyone to watch a video on the way that pigs are reared (sows are literally clamped horizontally in rearing pens so they don't roll over on their piglets) intensively and not think seriously about at least switching to free range. Even then, in a world that is rapidly running out of resources, it is hard to justify the expense of feeding grain to and watering animals - a vegetarian diet is far greener.
Finally, there are the health benefits. The USA, UK and West Europe have an adult population where the majority of adults and children are now over weight.
Having said all that, a healthy diet is no guarantee to health. I am vegetarian, weight about 140 lbs, run about 5 miles 5 days per week, don't drink too much and still I have high blood pressure!