“As long as we have this belief that obese people are lazy and lacking in discipline, it will be hard to get support for policies that change the environment, which are likely to have a much larger impact than trying to change individuals,” said psychologist Rebecca Puhl of the Rudd Center for Food Policy & Obesity at Yale University in New Haven, Connecticut.

That barrier to action is becoming clearer as the nation grapples with the costs of having two-thirds of adults overweight or obese. This week, an influential health panel proposed changes to an obesity-promoting environment, from farm policies to zoning, trying to shift the debate away from personal blame.

A new Reuters/Ipsos online poll of 1,143 adults from May 7 to 10 captures some of the prejudicial attitudes. Asked to identify the main cause of the epidemic, 61 percent chose “personal choices about eating and exercising”; 19 percent chose the actions of food manufacturers and the fast-food industry. The poll is accurate to within 3.6 percentage points. Because of the methods used to collect the data, accuracy is measured using a statistical measure called a credibility interval.

Reflecting the belief that the obese have only themselves to blame, 49 percent of respondents favored allowing insurers to charge obese people more for health insurance.