I'm vegetarian, because I've yet to hear a good argument for eating meat. The meat processing industry creeps me the hell out. The "animals eat animals, and I'm an animal. It's natural" attitude never made sense to me. Eating other animals is just as natural as dying from horrific, easily curable diseases, but not many prefer to stay natural when faced with the latter...if humans are not like other animals, what kind of argument is saying we should behave like them? =/ if we can do better, we should.
The health issues associated with vegetarianism I've never encountered. When I first changed my diet, I lost a big chunk of my excess body fat (about 15 lbs) and according to my blood work I'm healthier than ever. I don't take supplements. I don't even work out that much. I just have to think more about what I eat to make sure I get what I need. And fast-food is shit when it doesn't have all that delicious greasy meat in it so there's that gone =P
Overpopulation of animals wouldn't be a big issue if there weren't so many bred. That being said. I don't think there's anything wrong with killing and eating game like deer and rabbits that overpopulate naturally, as long as it stops there.
For the most part eating meat seems like unnecessary killing. Some of it's pretty tasty and if I truly had to eat meat to survive and be healthy, I would. But all the arguments against vegetarianism I've heard so far have been absolute bull. The idea that people need meat to live is wrong. I haven't eaten meat in 5 years, and I'm absolutely certain I'm not dead.