RAW DSer!
For DSer's animal protein is more bioavailable. If I were you, I would at least consider lacto-ovo (dairy and egg) vegetarianism. At least you could still get some animal based protein through eggs,milk and yogurt.
In fact, I was that type of vegetarian before my DS. I questioned whether I could use soy based meat substitutes at the pre-op seminar, and the surgeon said "You need to make a choice - vegetarian or obesity. You must use animal protein with this surgery" The body processes vegetable protein differently than animal protein.
I had eaten meat as a child, and actually becoming vegetarian was a last ditch attempt at losing weight. My issue was also complicated by steroids for lupus, which assisted in my massive gain as a pre-op. I guarantee you will be dealing with malnutrition before the year is out if you go completely vegan. Your digestive system is different now, and unless you really want a revision/reversal, it's changed for life.
Google short bowel syndrome. In simple terms, the DS acts the same way in terms of supplying nutrients and calories to the body, that's why DSers have to take such huge quantities of vitamin and mineral supplements.
Basically, if you don't feed your body what it needs, it starts eating itself, and that results in muscle wasting, osteoporosis and a whole host of deficiency-related disorders.