They're delusional, because most of them have been fat for most of their life. They literally don't know what their body is supposed to be like when fit. For example, dude I work with has decided to lose weight. He's 6-one or two tall and pushing 300 lbs. His ideal weight, according to him, is around 200 because "It's just how I'm built, pretty broad." Sure, if he lifted for a couple of years 200 would be ideal. No, he won't lift, because, "Exercise is hard." Fat fucks don't know shit about health.