Even healthcare professionals hold negative attitudes about the obese, studies show. Physicians often spend less time with an obese patient, for instance, and do not counsel them about a healthy lifestyle, perhaps believing it would fall on deaf ears.

Doctors and nurses who telegraph negative attitudes toward the obese can keep them from seeking treatment for diabetes, found a study led by Elizabeth Teixeira of Drexel University College of Nursing and Health Professions in Philadelphia.

“Patients are afraid of hearing, ‘you’re fat,’ or ‘just lose weight,’ as if it were that easy,” said Teixeira, a nurse practitioner specializing in diabetes. “I’ve had patients tell me they delay seeking care, even having their blood pressure or glucose checked, because they don’t want to be lectured.”

A 2010 study by scientists at Johns Hopkins University in Baltimore found that the fatter a patient, the more likely a doctor is to assume he or she is not taking medications as prescribed. That, other studies have shown, can keep physicians from prescribing needed meds, assuming they won’t be taken.

Taking all that data into account, it may not be surprising how reluctant people are to call themselves obese. In the Reuters/Ipsos poll, 14 percent of respondents said they are obese. Based on their self-reported height and weight, 26 percent are obese according to U.S. guidelines.

SHIFTING THE DEBATE

The belief that obesity reflects personal decisions implies that the solution, too, should be personal: Eat less, move more. But as the Institute of Medicine argued this week, the most effective way to combat obesity is to change the environment.

For average American adults, willpower is no match for “an environment in which we are constantly bombarded by food and food cues,” said David Kessler, former head of the Food and Drug Administration and author of the 2009 book, “The End of Overeating: Taking Control of the Insatiable American Appetite.” “Lecturing people doesn’t work.”

The IOM recommended building sidewalks to make it easier for people to walk, banning sugary drinks from schools and requiring 60 minutes of daily exercise in grades K-12, reducing portion sizes in schools and restaurants, and making low-cal choices widely available and as affordable as super-sized ice cream cones. Most important, it concluded, was changing the “messaging,” including the ubiquitous marketing of calorie-dense food.

Fat stigma makes those ideas ripe for attack by an industry that says how much to eat and move reflects individual choice. The restaurant- and food-industry-funded Center for Consumer Freedom called the IOM “arrogant and absurd” for suggesting “that Americans are too stupid to make their own food choices.” By proposing to keep unhealthy, calorie-dense food out of school lunch programs, it said, “food nannies” like the IOM are “flatly arguing against consumers having any choice in their snacks and meals.”

In the Reuters/Ipsos poll, respondents were almost evenly split over “government intervention” to reduce obesity, with 52 percent supporting it and 48 percent opposing it. There was greater support for specific steps, with 87 percent in favor of requiring 30 minutes per day of exercise in school.

ROOTS OF THE STIGMA

Psychologist Chris Crandall of the University of Kansas has found that young adults who stigmatize obesity tend to be more ideologically conservative, favoring traditional sex roles and capital punishment, his studies found.

“Particularly in America, self-determination and individual choice is a fundamental value,” he said. “We blame people for everything that happens to them - being poor, being obese. It’s the ‘just world’ idea that people get what they deserve.”

The stigma is less pronounced in countries such as India, Mexico and Turkey, whose cultures assign more collective responsibility for personal outcomes, Crandall found. His studies, going back to the 1990s, surveyed hundreds of people worldwide about how closely they associate obesity with adjectives such as lazy and stupid.

Americans also stand out in their conviction that hard work and determination lead to success, while failure is due to lack of effort.

“Being thin has come to symbolize such important values as being disciplined and in control,” said Yale’s Puhl. The converse: If someone is not thin, he must be lacking in those virtues.