Eric Oliver, a political scientist at the University of Chicago, said his first instinct was to laugh at the gas and drive-through arguments. But such claims often get wide attention, he says, and take on a life of their own.

“This is like, let’s find another reason to scapegoat fat people,” Dr. Oliver says.

At an annual meeting of the Obesity Society, one talk correlated obesity with deaths in car accidents, and another correlated obesity with suicides. Dr. Oliver, who attended, said no one in the crowd of at least 200 questioned whether the correlations were really cause and effect. “The funny thing was that everyone took it seriously,” he said.

Katherine Flegal of the Centers for Disease Control and Prevention also wryly cautions against being quick to link cause and effect. “Yes, obesity is to blame for all the evils of modern life, except somehow, weirdly, it is not killing people enough,” she said. “In fact that’s why there are all these fat people around. They just won’t die.”

The message in the blame-obesity approach, said James Morone, a political science professor at Brown University, is that it is so important to persuade fat people to lose weight that common sense disappears.

“Anything we can say to persuade you, we will say,” Dr. Morone added.

So is it working?

It doesn’t seem to be. Fat people are more reviled than ever, researchers find, even as more people become fat. When smokers and heavy drinkers turned pariah, rates of smoking and drinking went down. Won’t fat people, in time, follow suit?

Research suggests that the stigma of being fat leads to more eating, not less. And if reducing the stigma suggests a solution, that’s not working either.

“One hypothesis about getting rid of stigma is having more contact with the stigmatized group,” Dr. Brownell says. But with obesity, the stigma seems to be growing along with the national girth.