This is maybe a fair crticism of the logic insofar as it relates to diet pills or fad body wraps or something. Insofar as the argument in the OP relates to plus sized models, fat girl fashion labels and the "real women have curves" culture I think it's still correct. Someone selling size 42 pants needs you to be a size 42. A fat model needs to convince people that fat people can be beautiful.  Doctors don't benefit from keeping people sick. I mean, in the short term yes a sicker patient means more work, more bills. In the long term it means a reputation as the doctor that doesn't cure anything. That holds the same for diet pills but its way every fad exercise product like the Ab swing or ab circle pro disappears after 12 months and the same people start selling the ab puncher deluxe or something. Diet fads are a short game, doctors and trainers have to stick around forever. They're not constantly reinventing themselves to get ahead of their reputations as a scam. But the comparison doesn't work at all with plus sized clothes or fat models. Nobody is eventually going to go "hey... these clothes didn't make me lose weight!" because they never promised to.