There are many good health reasons as well as environmental reasons a person could eat a vegan or vegetarian diet. However, eating "meat" doesn't mean you're not healthy or won't lose weight.
And there's the thing about vegans, they can become morbidly obese. I do happen to know someone who is vegan and weighs over 275 pounds. French fries do qualify as vegan. Dark chocolate is vegan. We make an assumption that if a person is only eating veggies and grains, that they must be lean. Which in some cases, is true. but not all. If a person eats too much of anything, they'll gain weight.
So, don't worry that if you don't eat vegan you'll never lose weight or be healthy. That's just not true. I consider myself a reasonably healthy person and I do eat meat. I just don't eat it in the portions I did when I was overweight. I do try to watch my intake of red meat. I prefer chicken and pork.
Is it morally wrong to eat meat ? That's a whole different argument. You don't have to give up meat to be healthy, but you do have to watch your portions. When I was over weight, I used to think that a half a chicken was a normal portion size ! Honestly, I'd go to KFC and get their 4 piece meal all the time. That's a half a chicken, but that's what I considered dinner. Once I learned to get my portions in line, I did start losing weight.
I've also told people that if I went back in time and gave myself one piece of advice that would help me lose weight and be healthier, it would be to eat 6-9 servings of fresh fruit and veggies each and every day. You really don't have to be vegan to be healthy, BUT you should eat more veggies.... in general.
There's a lot of information out there and some of it is conflicting. Try not to worry, but do become an informed consumer as they say. Learn about nutrition. Have you read any of the great Spark articles on basic nutrition ? If not, start reading some of them. The more you learn, the less overwhelmed you'll feel.
I'm also going to recommend a book that will help sort things out as they say. It's by Michael Pollan and it's called the Omnivore's Dilemma. It's excellent. www.amazon.com/Omnivores-Dilemma-Natural-H
Here's one of his famous quotes about what to eat,"Eat food. Not too much. Mostly plants"