Getting healthy isn't just about eating well but also living well. Whether you are a a vegan, vegetarian or a meat eater, you need to exercise. I know fat vegetarians, especially people from India. Their cooking has a lot of oil, butter and sugar.
One thing a lot of people forget is that our ancestors used to do a lot more physical work and walk a lot more. Even if they were vegetarian / vegan, they would walk long distances.
If you can manage an all veg diet, that's great, but if you can't, then it's important to control your consumption and to exercise.