Misperception of Body Weight Poses Health Risks
Study Shows Dangers for Women Who Are Overweight but Consider Themselves to Be Normal Weight
By Kathleen Doheny
WebMD Health News
Reviewed by Laura J. Martin, MD


Nov. 22, 2010 -- Nearly one in four women who is overweight perceives her weight as normal, according to a new study.

The study also shows 16% of the normal-weight women studied had weight misperceptions, considering themselves overweight, says researcher Mahbubur Rahman, PhD, MBBS, assistant professor of obstetrics and gynecology and a senior fellow at the Center for Interdisciplinary Research in Women's Health at the University of Texas Medical Branch, Galveston.

There were dangers with both groups of what he terms "misperceivers," he tells WebMD. "Overweight women who were misperceivers are less likely to have healthy weight-loss behaviors." Those of normal weight who thought they were overweight, likewise, had unhealthy behaviors, such as using diet pills or smoking.

The study is in the December issue of Obstetrics & Gynecology.

"The fact that people misperceive their body weight was already known," says Rahman, so the new research echoes some previous information. But in his study, he also wanted to see if the body weight misperceptions influenced health behavior.
Analyzing Height and Weight Data

Rahman obtained height and weight information from the medical charts of 2,224 women, ages 18 to 25. 

The women answered questions about healthy weight-related practices in the 30 days prior -- including eating less, eating differently, or exercising. They also answered questions about unhealthy behaviors, such as the use of diet pills, use of diuretics, vomiting, laxative use for weight control, cigarette smoking, or skipping meals.

For the study, Rahman used the standard definitions for normal, overweight, and obese, with BMIs below 25 termed normal, those 25-29 overweight, and 30 and higher obese.

The women also answered questions about education, ethnicity, marital status, household income, employment, and Internet use.

The women were divided into four categories:

    * Overweight women who thought they were normal or underweight
    * Overweight women who knew they were overweight
    * Normal-weight women who thought they were overweight
    * Normal-weight women who thought they were normal or underweight


Weight Perceptions

In all, 1,162 women were overweight; of these, 895 considered themselves overweight and 267 did not.

The other 1,062 women were normal weight, with 892 of them perceiving themselves as normal or underweight but 170 thinking they were overweight.

Rahman noticed ethnic differences. African-Americans were more likely to underestimate their BMI while white and Hispanic women were more likely to overestimate it.

Overweight women who had gone to college and who used the Internet (presumably reading about weight information) were less likely than others to misperceive body weight.

The dangers? Those who didn't perceive their weight correctly, Rahman says, were more likely to engage in unhealthy behaviors. The overweight women who thought they were normal weight didn't cut back on food intake, for instance.

The normal-weight women who thought they were overweight were more likely to use diet pills or diuretics or smoke cigarettes.

One bright spot: Among overweight women who knew they were overweight, 35.9% said they ate differently or less in the past 30 days, in attempts to shed weight.

Rahman says the finding that so many overweight women view their body weight as normal reflects the ''fattening of America."  "They see overweight people everywhere they go," he says, and that becomes, for them, the new norm.

Rahman worries the trends will continue "unless we see a rapid change in the mind-set of people."
Second Opinion

The ''fattening of America'' explanation given by Rahman for why so many overweight women think they are normal weight makes sense to Cheryl Rock, PhD, RD, a professor of family and preventive medicine at the University of California San Diego School of Medicine, who reviewed the findings for WebMD.

"It might very well be if you look around and you're not fatter than anyone you hang out with, then you don't perceive yourself as being overweight," she says. "You look like everyone else."

Doctors should take note of the findings, she says, and ''have an eye open to those who are overweight and don't think they are," offering weight loss counseling.

"Find out your BMI,'' Rahman advises. You can ask your doctor to tell you, or you can plug in your height and weight on the BMI calculators widely available online.