I have been vegan for a few months, before that I was vegetarian for 18 years.
I did lose weight and continue to do so, of course I don't eat processed foods very often. I think that is the important part. I eat as much food as I want because I have given up the foods I know don't love me.
I have Spatone if I need it for iron, b12 is important as its difficult to get these days ( even for non vegans).