Joseph, does that include taking two wives, divorcing a woman b’al korchah, doing yibum instead of chalitza, becoming a glutton, eishes yifas toar? There are things in the Torah which are a reshus, and not obligatory. There is a concept of naval birshus hatorah. Just because the Torah permits something, does not mean it recommends it in any way. The same was true of the mayseh meraglim. We had permission to send them, but it was no mitzvah to do so.
A person can elevate himself above the bare minimum, although the Torah does not obligate him to do so. Each person must decide based on what he considers his role in life. If being a vegetarian would leave him with insufficient energy to do certain types of chesed, then he should probably choose to do chesed, and not go vegetarian. However, if he feels that he can function OK, and wants to be kinder to animals than what is required, that is also praiseworthy.