Full Idea
To eat or drink indiscriminately until one is full to bursting is to exceed in quantity one's natural limit, since the natural desire is merely a replenishment of the deficiency.
Gist of Idea
To eat vast amounts is unnatural, since natural desire is to replenish the deficiency
Source
Aristotle (Nicomachean Ethics [c.334 BCE], 1118b21)
Book Reference
Aristotle: 'Ethics (Nicomachean)', ed/tr. ThomsonJ A K/TredennickH [Penguin 1976], p.138
A Reaction
This illustrates nicely Aristotle's need for a concept of 'unnatural' to support his theory of virtues. A glutton could claim to have an enormous deficiency, and to counter that we must say that being overweight is unnatural. Etc.