Discrimination against obese people may have a direct impact on their physical health, suggests research from Purdue University in Indiana.

"Obesity is a physiological issue, but when people have negative interactions in their social world — including a sense of being discriminated against — it can make matters worse and contribute to a person's declining physical health," noted the study's leader, Markus Schafer.

About a third of the severely obese people in the U.S. questioned for the study reported that they faced some form of discriminatory experience.  "It seems that many people are internalizing the prejudice and stigma they feel, and it contributes to stress, which ultimately affects their health," Schafer said Thursday.

The Centres for Disease Control and Prevention report that 34 per cent of U.S. adults are overweight, meaning their body mass index (BMI) is between 25 and 29.9, and another 34 per cent are obese, with BMIs of 30 or higher.  Twenty-four per cent of Canadians are considered obese, according to new statistics released on Wednesday.

"As expected, those who were obese fared worse in overall health when they were followed up with 10 years later," Schafer said. "But we found there was a difference among those who felt they were discriminated against and those who didn't." 

About 11 per cent of those who were moderately obese and 33 per cent of those who were severely obese reported weight discrimination.  These people had the sharpest decline over time in their functional abilities, such as the capacity to climb stairs or carry everyday items.

The co-author of the study, Kenneth Ferraro, noted that weight discrimination receives little attention despite the prevalence of weight issues in the United States. "As the rates of obesity rise in this country, one might expect that anti-fat prejudice would decline," he added.

The Purdue team's findings are published in the March issue of Social Psychology Quarterly. 

The study compared body mass indexes to people's health and perceptions of weight discrimination. The data was extracted from a survey of more than 1,500 people aged 25-74 who were questioned in 1995 and again in 2005 about issues related to aging and health equality.