Yeh, I was vegetarian for a while. Worked well for about 5 years then I started loosing too much weight. Most of my meals are still vegetarian, but when I finish a meal and ask "where's the beef" I know it's time to eat some animal food.
The problem I've seen with many unhealthy vegetarians is that they don't understand how to acquire adequate amino acids. They stop eating meat and start eating Ragu on pasta or some such. Won't work.
Eating veggie sources of protein is more efficient- the body doesn't have to labor to break meat protein down into aminos- but a lack of aminos results in poor health. Ever notice how many have bad teeth?
Peter D'Adamo MD has an interesting take on it, which explained for me why some do well and some don't and it's based on blood type.
Os (Omnivores- majority) apparently do better with more animal food, veggies/fruits, and little or no grain. As (Agrarian) tend to be the most successful with vegetarian fare. Bs (Barbarians) have the most flexibility, everything in moderation. ABs- the most recent type, a composite of A and B, more prone to cancer therefore should be very selective with the quality of food they consume.
I'm a B+ and found this to be true for me. I think the key is moderation. Humans are omnivores, but that doesn't mean they'll be in the best health if they eat a quarter to half pound of meat per meal. Some consume their daily limit for calories/fat in just one meal. It's why we have such issues with obesity. The most well fed, undernourished country on the planet.
Interesting, or curious is that many Os desire to be vegetarians, and many As would prefer to eat meat.
Our current food production system is not sustainable and is leading us toward an unhealthy food supply- genetically engineered foods packed with chemicals and no nutrition.
We may do better with fewer people on the planet, but with sustainable agriculture practices we would have no problem feeding everyone, and then some. I think Permaculture holds the most hope for sustainability. Forget the guys name, but one model of a well designed PC homestead was able to accomodate and feed 100 people on just 15 acres. Nothing complicated, just emulating nature with a good design.
Here's a few links.
http://permaculture.org.au/Scroll down and click on Greening the Desert Video
http://www.foodnotlawns.com/Food Not Lawns
http://news.independent.co.uk/world/ame ... 217550.eceCuba's Green Revolution- Organoponicos