> If your body fat percentage is high enough (25% or more for example) it is even possible to gain muscle on a calorie deficit. Many studies have shown it's possible to lose fat while gaining muscle for such individuals.

Being a vegan it is very difficult to get enough protein needed to maintain the existing muscle mass, not to mention grow muscles at 1500 calories per day. That's below base for most men even with a lifestyle that does not include anything other than NEAT.