The Internet Oracle has pondered your question deeply.
Your question was:

> O great and powerful Oz, can you . . . .  What?  Wrong chamber? Oh,
> sorry.
>
> O great and powerful Oracle, whose boots I am not fit to lick, I
> beseech you, pray answer me this question which has vexed me, lo these
> many years.  How does Pac-Man eat all those dots?  He never grows
> bigger and has no visible excrement, yet he just keeps on eating more
> and more of them.
>

And in response, thus spake the Oracle:

} This is because Mr. and Mrs. Pac-Man are getting more than enough
} exercise. Did you notice how much they have to run around in every
} game? If you would run that many miles every day, you would be also
} very lean and fit.
} No excrement you say? You never looked inside of one of those game
} boxes after a few years ... full of dust! That are the excrements of
} Pac-Man.

Notes: I've asked this question three times over a long period of time. I finally decided, when I got the answer above, that it would do and I'd retire the question. But if you didn't like that response, below are the others I received.

First . . .

} What else can he do? He ain't got no arms, or legs, or,
} well, anything else. . .

Then . . .

} About my boots...
} Darn right you are not fit to lick them.  You don't know how
} to move fast enough to avoid being kicked in the face.  Not
} to mention that your saliva burns holes in leather.  Yecch.
}
} About PacMan...
} It's his saliva.  Same sort of stuff you have, very corrosive.
} Turns everything he eats to invisible smoke.  Watch next time,
} and you'll notice that you can't see it.  That's how you can
} tell it's invisible.