(PhysOrg.com) -- When it comes to losing weight, perception is not always reality - in fact, it's often a major hurdle.
In a new study, nearly one in four adults who were either overweight or obese did not believe they had a weight problem, and as a result did not see a need to improve their health.
With nearly 70 percent of Americans classified as either overweight or obese, the findings have serious implications for how to target efforts that will help Americans lose weight, researchers said.
"It's often said that the first step in improving a problem is believing that you have one. That's particularly true for obesity," said Gary Bennett, associate professor of psychology and neuroscience at Duke University and senior author of the study.
"A sizeable proportion of obese Americans don't accept that they have a weight problem. This group is less likely to practice healthful behaviors that will help them lose weight and improve their health."
The researchers used data from the 2003-2006 National Health and Nutrition Examination Survey, conducted by the Centers for Disease Control and Prevention.
They examined associations between weight misperception and several weight-related attitudes and behaviors, including wanting to weigh less, having tried to lose weight, dietary intake, and physical activity among overweight and obese adults in the U.S.
The overweight and obese men who misperceived their weight were 71 percent less likely to want to lose weight and women were 65 percent less likely, according to the study, which appears online in the International Journal of Behavioral Nutrition and Physical Activity. (View the report at http://www.ijbnpa.org/content/8/1/20/abstract )
In addition, researchers found that 60 percent of men and 56 percent of women with misperceptions about their weight were less likely to have tried to lose weight within the past year, compared to those who accurately perceived themselves as overweight.
The findings also showed that people with misperceptions about their weight were more likely to continue with habits that will only increase their weight, such as not exercising. Extremely obese individuals face elevated risks for type 2 diabetes, cardiovascular diseases and some types of cancer.
Researchers said most studies on weight misperception only focus on socio-demographic factors, such as gender and race/ethnicity, and not on attitudes and behaviors.
"Our study is among the first to show that weight misperceptions hinder weight loss and control, which is important on its own but also because these data are nationally representative," said Dustin Duncan, lead author of the study who recently completed his doctorate in social epidemiology at the Harvard School of Public Health.
Results varied by race and gender, and blacks who misperceived their weight were particularly less likely to have tried to lose weight, researchers said.
"This was particularly concerning because U.S. blacks have the highest rates of obesity and obesity-associated health problems," Bennett said. "Compared to those in other groups, blacks are more likely to misperceive their weight and less likely to attempt weight loss."
The study said only about 40 percent of respondents in the sample reported being told by a physician or health professional that they were overweight. Several studies have shown that attempts to lose weight tend to increase after a medical professional advises obese patients to do so, researchers said.
"These findings show that it's important for health care providers to consistently diagnose obesity and counsel their obese patients about effective weight-loss strategies," said Bennett, who also holds positions in the Duke Global Health Institute and the Duke Center on Biobehavioral and Social Aspects of Health Disparities.
Researchers said the clothing industry can also help by eliminating "vanity sizing" or size inflation, in which size numbers scale down over time, so a size 14 becomes a size 10. They also believe social norms related to weight could be a reason for the misperceptions.
"It is also necessary for us to understand why these misperceptions exist in the first place, to determine the best strategies for preventing and reducing these misperceptions," Duncan said. "We plan to investigate some of these hypotheses in follow-up studies."
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