Back in the middle ages, when the patriarchal power structure was even more powerful than it is now, being fat was considered as beautiful among women.
I don't know about beautiful but I think it was a sign of wealth. I remeber reading that somewhere.
Yes, you're right. Wealthy people had the luxury to eat themselves fat in those days. However, if you look at the paintings from the renaissance, you can not find any size zero women. "Fat" and wealthy women were the beauty ideal back then.
You are absolutely right, just look at the ass on the Mona Lisa.