Pizzatarian

An individual who, by choice or divine culinary calling, subsists primarily or exclusively on pizza.
Someone who believes that the major food groups are cheese, sauce, crust, and toppings.
A devoted disciple of the Church of Deep Dish and the Holy Slice.

Example 1: "Mike hasn't eaten anything but pizza for the past week. Dude's turning into a full-blown pizzatarian."

Example 2: "Why go vegan or keto when you can be a pizzatarian and live the cheesy dream?"