As a woman whose height and weight put me in the obese category on the body-mass-index chart, I cringed when Michelle Obama recently spoke of putting her daughters on a diet. While I’m sure the first lady’s intentions are good, I’m also sure that her comments about childhood obesity will add yet another layer to the stigma of being overweight in America.

Last August, Dr. Delos M. Cosgrove, a cardiac surgeon and chief executive of the prestigious Cleveland Clinic, told a columnist for The New York Times that if he could get away with it legally, he would refuse to hire anyone who is obese. He probably could get away with it, actually, because no federal legislation protects the civil rights of fat workers, and only one state, Michigan, bans discrimination on the basis of weight.

Dr. Cosgrove may be unusually blunt, but he is far from alone. Public attitudes about fat have never been more judgmental; stigmatizing fat people has become not just acceptable but, in some circles, de rigueur. I’ve sat in meetings with colleagues who wouldn’t dream of disparaging anyone’s color, sex, economic status or general attractiveness, yet feel free to comment witheringly on a person’s weight.

Over the last few years, fat people have become scapegoats for all manner of cultural ills. “There’s an atmosphere now where it’s O.K. to blame everything on weight,” said Dr. Linda Bacon, a nutrition researcher and the author of “Health at Every Size: The Surprising Truth About Your Weight” (Benbella, 2008). “If we’re worried about climate change, someone comes out with an article about how heavier people weigh more, so they require more fuel, and they blame the climate change crisis on fatter people. We have this strong belief system that it’s their fault, that it’s all about gluttony or lack of exercise.”