I don't believe there is one diet that is perfectly healthy for all, because we are all different.When I went semi-vegetarian a couple of years ago, I was hungry all the time, and in spite of a regular exercise program, I gained 16 pounds. Gained weight on salad, chicken, fruit, yogurt, cereal and vegetables. Ate no sausage or cheeseburgers or ice cream.
When I switched back to eating more lean meats and less bread and pasta, the weight came off and I am not hungry all the time.
Whoever up above said that a veggie diet is cheaper... come shopping with me one day and you may change your mind. Good vegetables are expensive down here in Tennessee.
I say, if you want to try it, try it. Somebody mentioned vegetarian cooking is better now than it ever has been. And the meat-substitute soy products are much better too.
Good luck!