A vegetarian (or even vegan) diet is often suggested to yogis, people who practice yoga. Does veganism have any positive effect on the practice of yoga, compared to a vegetarian or omnivorous diet? Why? Is it for spiritual (e.g. karma) reasons, or something related to body flexibility, etc.?
As some people suggested in comments, yoga is very broad term. You are probably referring to physical activity of stretching in variety of poses. For a person practicing yoga, becoming vegan part of yoga itself. It has positive effects on your body so it has to have positive effects on your yoga and well being. It's simply very natural to become free of animal products (if one has the chance). Everyone might have different reasons which have convinced them at first to change diet. But I would just argue, that it is natural process of a person seeking better self.