In what ways is Gregor “dehumanized” by his isolation?

From the text:

Out of consideration for his parents, Gregor wanted to avoid being seen at the window during the day, the few square meters of the floor did not give him much room to crawl about, it was hard to just lie quietly through the night, his food soon stopped giving him any pleasure at all, and so, to entertain himself, he got into the habit of crawling up and down the walls and ceiling. He was especially fond of hanging from the ceiling; it was quite different from lying on the floor; he could breathe more freely; his body had a light swing to it; and up there, relaxed and almost happy, it might happen that he would surprise even himself by letting go of the ceiling and landing on the floor with a crash. But now, of course, he had far better control of his body than before and, even with a fall as great as that, caused himself no damage.