These three short sentences paint a picture of excess gone sour. The opening line, "Satiation dulls," says that being completely full doesn't bring pleasure. It numbs us. Instead of enjoyment, there is a flat, heavy feeling where appetite used to be.
The next two lines make that idea physical and unpleasant. "Bloated faces" suggests people swollen with too much food, drink, or whatever else they've been consuming. Then comes the most jarring image: mouths "expel what should pass elsewhere." The poem doesn't name what comes out, which makes it more uncomfortable. Mouths are doing the wrong job, as if the body, and perhaps the people themselves, have lost track of what goes where.
The speaker sounds disgusted and detached, observing rather than joining in. The clipped, blunt sentences feel like a cold stare. The mood is queasy and critical, a warning that overindulgence leaves us ugly and empty, not satisfied.