Can a Catholic be a vegetarian, not eating meat, fish, or eggs? What is the attitude of the Church on this diet? Some Catholic saints were vegetarians, I understand.
It is perfectly fine for a Catholic to be a vegetarian, although I should mention that some vegetarians eat eggs. There are various kinds of vegetarianism and those who drink milk and eat eggs are called lacto-ovo vegetarians. Those who do not are called vegans.
The only caveat here is that a Catholic vegetarian should not presume that it is sinful for Catholics to eat meat. The Church allows animals to be used for just purposes, one of which is for food.