He knows he's fat and he knows it's bad to be fat.  He's saying he may or may not be a "ham" because on FPS a "ham" is a fat person who acts badly, whereas a fat person who behaves well is just a person who happens to be fat, and who would be better off thin but still deserves to be respected (and thus not to be called insulting names like "hambeast").  It's a problem of jargon. Beneath this problem is a weird culture of tolerance for obesity at FPS...  those people don't seem to truly want things to change, to my perception; they seem to mainly just want to read and tell stories.  They like the idea of fat people working to become thin, but many of the fat posters there don't actually become thin, it seems...  I dunno.  There's something unhealthy going on there I think, but this ham/non-ham question in itself is not exactly it.