How did Kafka describe alienation in "A Hunger Artist" ?

The Hunger Artist is physically isolated from the world via his
cage, but he is also isolated from the world in that only he can understand the seriousness and
the importance of his "art." Although his art is to be displayed to the public, he has no
personal life other than his own isolation. This is a symbolic but also a literal image of the
"starving artist" - the idea that the artist must suffer for his/her work, and that the artist
does it for the sake of art/not for money; thus, with no money, the artist may starve. With the
Hunger Artist, his starvation and dedication to his art is mostly self-imposed, just as any
artist is when he/she chooses to be an artist. But the Hunger Artist also notes that he fasts
because he has never found a food he likes, implying that he was literally seeking nourishment
and found none; so he doesn't find material nourishment. And he doesn't find public nourishment
because no one understands him. And he doesn't find spritiual or mystical nourishment (until the
end) because he is never alowed to really push the limits and flirt with death: fast beyond 40
days.

The fleeting nature of fame is a theme here as well. When the
audience starts to ignore him, his isolation is of course increased, which makes him even more
desperate in his fasting and eventually leads to his death.

Other
than the final fast, the hunger artist must also stop after 40 days because that's when people
lose interest. When he did stop every 40 days, he "sells out" by ensuring that he will eat and
live to fast and sell out again. So, during his last fast, he is completely isolated in the fact
that he is not understood and now he is not part of the economic institution of art. So, he is
out of contract and no longer even noticed, hidden under the straw. I would call this total
isolation, but the real complete isolation is his death.

In the end,
he achieved no material (food), public (understanding), or artistic (spriritual)
nourishment.

Check out the second link below for other
interpretations of isolation of the artist in the modern world.