How does Zusak let us know Max is starving?

Zusak uses a poem. We learn that Max has been hiding in a room for for days without any food. A friend enters briefly and gives Max some food and a book (Mein Kampf), which secretly contains a card, map, key, and directions. Max devours the food he is provided with.

We will travel a little, to a secret storage room, and we will see what we see.
A GUIDED TOUR OF SUFFERING

To your left,

perhaps your right,

perhaps even straight ahead,

you find a small black room.

In it sits a Jew.

He is scum.

He is starving.

He is afraid.

Please—try not to look away.

He had eaten only the foul taste of his own hungry breath for what felt like weeks, and still, nothing.