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We hear it all the time: Americans — especially women — are constantly dieting, trying to lose weight to look thin. America's obsession with thinness and weight loss has been implicated in concerns over eating disorders; with most girls and women already working so hard to lose weight, seeing idealized thin (and airbrushed) celebrities may push them into dangerous dieting.

Parents and health officials also lay blame on the fast food industry for not offering healthy choices on their menus. But new research suggests that Americans' insistence that they want to lose weight and eat healthy is largely a myth.

According to Associated Press reporter Christina Rexrode,

Americans talk skinny but eat fat. No matter that Michelle Obama has been on a crusade for a year and a half to slim down the country. Never mind that some restaurants have started listing calories on their menus. Forget even that we keep saying we want to eat healthy. When Americans eat out, we order burgers and fries anyway. … While 47 percent of Americans say they'd like restaurants to offer healthier items like salads and baked potatoes, only 23 percent tend to order those foods, according to a survey last year by food research firm Technomic.

In contrast to Bridget Jones and popular opinion, most Americans — including women — are fat and not particularly concerned about doing anything about it. Two-thirds of American adults are overweight, and more women than men are obese, yet fewer than one-quarter are dieting at any given time. Only a minority of Americans eat a healthy diet, and fewer than one-third get regular exercise.

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So why do people say they want to lose weight, but make little or no effort to do it?

Part of the answer may lie in the fact that people may not realize that they're overweight and therefore don't think they need to diet or choose healthy foods. According to research published last year, nearly 40 percent of overweight women believe themselves to be thinner than they really are.

The researchers found that 36.8 percent of overweight women (and 10.5 percent of obese women) believe themselves to be underweight or of normal weight. As lead author Dr. Mahbubur Rahman noted, "greater misperception of body weight in this group means less weight loss behavior."

The study also found that despite the popular assumption that most women think they are too fat, only 16 percent of normal-weight women in the study perceived themselves as overweight. The study, "Self-Perception of Weight and Its Association With Weight-related Behaviors in Young, Reproductive-aged Women," was published in the December 2010 Obstetrics & Gynecology.

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Another study published earlier this year contradicts the popular idea of weight-obsessed women who will do anything to look perfect: Overall, the majority of the women surveyed said they would not sacrifice anything at all to achieve their ideal body shape and weight.

They were not interested in dieting, exercising or even paying money to attain their ideal weight. The survey, conducted for a British eating disorder organization called The Succeed Foundation in partnership with the University of the West of England, found that fewer than one-third of women reported that they would trade at least a year of their lives to be at their ideal weight.

The simple fact is that losing weight just isn't that important to most people. If Americans were serious about wanting to lose weight, they would choose to eat a healthy diet and exercise more.

The widely heard claim that "diets don't work" is a dangerous myth. Healthy diets only work if you eat them — just as exercise equipment only gets you in shape if you use it.