If you avoid meat because you do not want the nutrients or is allergic, it is a diet. If you avoid meat because you find it wrong, it is a philosophy or religio

If you avoid meat because you do not want the nutrients or is allergic, it is a diet. If you avoid meat because you find it wrong, it is a philosophy or religion. If the question is about belief, I would not consider "vegan" a diet in any possible meaning of the word. (The above does not state that I find veganism to be wrong—rather, it merely classifies the ideology.)