Also its important to take into account that the term "gluttony" can be a reference to over-indulgence in material items, wealth, and extravagance. This is how I've understood the term, not just related to eating the entire yummy pizza.
Its always wanting more, bigger and better, and never feeling satisfied with the "things" you have.
Although there is a focus on materialism in other parts of this world, I certainly notice it more when I am in North America. However, we all get caught up in this from time to time, no matter where we are from.