a meal unto itself

A food item, especially a snack, appetizer, or side dish, that is so filling or rich that one does not need anything else to eat. Wow, that appetizer seemed like a meal unto itself. How on earth am I going to have room for the main course? We've created a protein bar so packed with energy that it is basically a meal unto itself. That triple-decker sundae is basically a meal unto itself, so why don't we split it between the three of us?