What is it called when a person only eats one food all of the time?

I know a guy who all he eats is pizza. Breakfast, lunch and dinner. Pizza.





We had a cookout, and when he came, he brought a pizza for him to eat.|||boring! someone like that is afraid of change, possibly obsessive compulsive. I have seen a criminal minds episode where a serial killer did this, but then again, if they are on a strict diet, that is perfectly sane and normal. For example, many people can't eat gluten, or wheat, whatever it is. Also, they may have had food allergies that freaked them out and since none have happened from this particular food, then maybe that's why:)





The man loves pizza apparently?!! I do too, but i would be a blimp if i ate it that much:) Maybe ask him to bring a mexican pizza next time lol!|||Fat