I agree with the above posters. Get bloodwork done, because IMO ingesting adequate Iron, B-12, EAA's, Zinc, Vitamin D, Chromium (greater than normal because of high CHO's effect in insulin processes), and Cholesterol (really only important for an anabolic minded individual) is difficult with a vegan diet unless meticulously planned.
Just as a heads up, the text that follows doesn't necessarily constitute scientific fact, my statements are conclusions I've reached through my own observations. These are my own personal views and if someone has contradictory science I welcome being corrected.
IMO you need get to a favorable body fat %, i'd say 8-13%. The stresses a CHO heavy diet imposes on insulin production and secretion I think are a recipe for developing diabetes without prudent diet planning. The high fiber and (i'm hoping) plant based oil's that would be ideally consumed will help idealize insulin secretion, but it is my view that a high starch intake is detrimental. If I was forced into becoming vegan because there was no animal meat left on the planet, I'd shoot myself. Just kidding. But the majority of starches (once again, IMO) should not be eaten unless their is enough adequate fiber and other macronutrients to slow down processing into the blood stream (I'm not a big fan of starches BTW). I know a few vegetarians who, while don't eat meat by definition, struggle with unwanted body fat even while practicing calorie restriction. I'm of the mind that the overabundance of starches in their diet effects insulin so negatively they can't lose the fat, instead maintaining their fat stores while catabolizing their muscle tissue.
My advice is to modify your diet so that you reach a healthy body composition and then take special care to minimize insulin response in your meal planning. Play around with higher plant oil intakes, try up to a fat% in your macros of 30%. If you start to gain unwanted fat, then ease back down. Genetics are going to be the main factor in determining how your body responds to different macro intakes, personally I have the best composition with ~30% Fat/ +30% Protein/ ~40% CHO. Focus on creating a diet supplying an abundance of amino acids from complimentary proteins while minimizing insulin responses.
Most people who practice the vegetarian lifestyle lack the necessary nutritional knowledge to have optimum health. If you have any questions or need to learn, you've come to the right place and I'm more then willing to share my knowledge. If you are serious about losing weight and putting on serious muscle mass, then I would seriously reevaluate your motivations for not eating meat. I'm not trying to convert you, but understand it will be extremely difficult if you are a practicing vegan. If you are lacto, ovo, or a combo, it will be much easier.