Many young women may not realize whether their weight is healthy or not, which could have consequences for their diet and lifestyle habits, a new study finds.

Researchers found that among more than 2,200 women ages 18 to 25 seen at several Texas reproductive-health clinics, “weight misperception” was common among both normal-weight and overweight women.

Of the 1,062 study participants who were normal weight or underweight, 16 percent believed themselves to be overweight.

Meanwhile, one-quarter of heavier women - including 37 percent of overweight women and 10.5 percent of obese women - believed their weight was normal or too low.

The problem with such misperceptions, the researchers say, is that they may lead to less-than-healthy lifestyle habits.

Indeed, the study found that normal-weight women who felt they were overweight were more likely than those with accurate perceptions to try unhealthy weight-control tactics - like skipping meals, abusing diuretics (water pills) or using diet pills.

Overall, 36 percent of normal-weight women with mistaken impressions said they’d taken one of those extreme measures in the past month, versus 19 percent of normal-weight women with accurate perceptions.

And for their part, overweight women who perceived themselves as normal-weight were less likely to try healthy approaches to weight loss - like curbing calories and getting regular exercise. One-third of those with misperceptions said they’d tried a healthy tactic in the past month, versus 45 percent of overweight women with accurate perceptions of their weight.

On the positive side, though, overweight women who believed they were normal-weight were also less likely to report any unhealthy weight-loss measures.

The findings, reported in the journal Obstetrics & Gynecology, suggest that weight misperceptions are common and could have significant public health implications.

“Since one in four overweight and obese women think that they are normal weight, it is a big obstacle to obesity prevention efforts,” lead researcher Dr. Mahbubur Rahman, an assistant professor of obstetrics and gynecology at the University of Texas Medical Branch in Galveston, told Reuters Health in an email.

“We think that many people do not know their weight status, and the range of normal-weight, overweight and obese categories,” Rahman said.

However, he added, it is simple to find out into which category you fall.

The standard method for determining weight category is to measure one’s body mass index (BMI), which assesses weight in relation to height. Rahman noted that people can measure their own BMI by dividing their weight (in kilograms) by the square of their height in meters.

For people with less confidence in their math skills, there are also online BMI calculators like the one on the National Heart, Lung and Blood Institute’s Web site (http://www.nhlbisupport.com/bmi/). You need only know your weight in pounds and height in feet and inches.

A BMI of 18.5 to 24.9 is considered normal. A BMI of 25 to 29.9 falls into the overweight category; and people with a BMI of 30 or higher are in the obesity category.

According to Rahman, the findings also point to a need for doctors and other health providers to assess younger women’s perceptions of their weight and offer them guidance based on those beliefs. They should also ask women about any unhealthy weight-control measures they may be taking, he noted.

The current findings are based on 2,224 18- to 25-year-olds seen at any of five publicly funded reproductive-health clinics in Texas between 2008 and 2010. So the group is not representative of U.S. women in general.

However, some earlier studies have looked at a broad sample of U.S. women. In one recent study, researchers examined data from a government health survey conducted between 1999 and 2006. In that study, 22 percent of overweight women considered themselves normal-weight, as did five percent of obese women.

Rahman’s team also found that weight misperceptions varied by race. Overweight African-American women were nearly three times as likely as overweight white women to consider themselves normal-weight. There was no significant difference between white and Hispanic women.

That racial difference, the researchers note, is in line with previous research on weight perceptions.

SOURCE: Obstetrics & Gynecology, December, 2010.