It's just bullying. Plain and simple. Making someone else feel small to boost one's own ego is wrong. My younger brother was pudgy when he was 13 or 14 -- pretty much just baby fat. He was picked on constantly but now that he's 16 years old and 6' 4" and over 200 well-muscled pounds, no one picks on him anymore. He remembers what it was like to be bullied and (he's such a gentle soul) he tries to help other people deal with being picked on.