Discriminating against a person because of their weight may actually increase the chances of that individual becoming obese, researchers report.
People who experienced this so-called "weightism" are two and a half times more likely to become or stay obese later on, the researchers added.
"Discrimination is hurtful and demeaning, and has real implications for physical health," said lead researcher Angelina Sutin, an assistant professor of psychology at Florida State University.
"In the case of weight discrimination, people often rationalise that it is OK to do because it will motivate the victim to lose weight," Sutin said. "Our findings suggest the opposite."
The report was published July 24 in the online journal PLoS One.
One expert said the blows to self-esteem make it harder for people struggling with their weight to feel they can make meaningful change.
"I have worked for many years to help my clinical colleagues provide constructive and compassionate weight-management counseling," said Dr David Katz, director of the Yale University Prevention Research Center.
"Obesity bias, or weightism, by medical professionals or our society at large is the literal addition of insult to injury," he said.
Weightism does the predictable: It adversely affects self-esteem, and undermines the effort required to control weight, Katz said.
"In my own work, with adults and kids alike, I have found that the heavy burden of such insult needs to be set down first, and the pounds readily follow," he said.
Some 80% of adults in the United States are overweight or obese, as are a rising percentage of children, Katz said.
"It's time to address overweight with a lot more understanding, and curtail that injury," he said. "There is no place in the mix for the insidious harms of insult and prejudice."
To measure the effect of weightism, Sutin and her colleague Antonio Terracciano, an associate professor of geriatrics, compared the height and weight of more than 6000 people in 2006 and again in 2010.
They found that those who experienced weight discrimination in 2006 were two and a half times more likely to be obese in 2010.
The effect of weightism was independent of other factors, such as age, sex, ethnicity or education, the researchers found.
Simon Rego, director of psychology training at Montefiore Medical Center and Albert Einstein College of Medicine in New York City, said that "this study suggests that weight discrimination may have consequences not only on mental health – increased vulnerability to depression, lower self-esteem – but physical health as well."
"If true, interventions on both individual and public levels should be considered," Rego said.
"These might include psychologists working with obese patients to teach them more adaptive ways to cope with discriminatory behaviours and manage their weight, as well as policy makers targeting the public via media campaigns to raise awareness of deleterious effect of discrimination," he said.
Sutin added that weightism is a "vicious cycle".
"In addition to the well-known emotional and economic costs, our results suggest that weight discrimination also increases risk of obesity," she said. "This could lead to a vicious cycle where individuals who are overweight and obese are more vulnerable to weight discrimination, and this discrimination may contribute to subsequent obesity and difficulties with weight management."
Although the study showed an association between weight discrimination and obesity, it did not prove a cause-and-effect link.
For more on obesity, visit the US National Library of Medicine.