Little White Lies
Educated white women are most likely to lie about their weight and height.
While most people often exaggerate their height while diminishing their weight, some of us are more likely to be dishonest than others, says a study that examined how demographics affect self-reports of BMI (Body Mass Index). Whites are more likely to under-report their BMIs (meaning they will report a lower BMI than their true measurement) than blacks or Hispanics, reveals lead study author Ming Wen, PhD., associate professor of sociology at the University of Utah.
Looking at education, ethnicity, weight status, age, and SES, Wen and her research team determined that men and women from all ethnic groups overestimate their height, and that women from all groups under-report their weights more often than men do. However, white women were more likely to under-report their weights than black and Hispanic women.
Wen says that she, her colleague Lori Kowaleski-Jones, PhD., and the team were inspired to examine differences in BMI self-reporting and demographics because most studies on obesity involve participants’ self-reports of weight and height.
“We were wondering how accurate these self-reports are if most reported prevalence rates of obesity are based on self-reported data,” Wen explains. “We were also wondering what socio-demographic factors were particularly linked to the response bias in BMI so that we should be particularly careful when using self-reported BMI for these socio-demographic groups.”
In addition to sex and ethnic differences in self-reporting, Wen and the researchers found variances according to education levels. Women who were college-educated were also more likely to report lower BMIs than they actually were.
Women, Wen says, are generally more likely to feel social pressure to be slim, and pay more attention to their appearance than men, but college-educated women have more factors—such as social pressure—to consider.
“Given the bombarding messages about the detrimental effects of obesity and a social desire of having lean body, women are probably more likely than men to want to have an ideal body image,” Wen maintains. “Meanwhile, education, regardless of gender, contributes to individuals’ efficiency of processing information. Partly because of this, education is strongly linked to healthy lifestyles like exercise and non-smoking.”
“So more educated people are more keenly aware of the benefits of having a normal weight and thus are facing stronger social desires of maintaining a normal weight,” she adds. “They, therefore, may have a stronger tendency to under estimate their BMI to conform to that social norm or desire of having a normal weight.”
Moreover, education is actually linked to lower likelihood of obesity.
“Considering educational levels are often comparable among friends, better educated individuals are more likely to have better educated friends who tend to have normal weight,” Wen speculates. “This adds to another layer of social pressure, which is not just from society in general but also from your close social circle.”
Income had no effect on how men reported their BMIs, while it had a marginal effect for women, with higher-income women slightly more likely to under-report their BMIs. However, Wen says, the income effect was much weaker than that of education.
While researchers expected the overall study results to indicate these findings, there were a couple small surprises, Wen notes. The amount of under-reporting was smaller than expected, but Wen says, that may be due to the nature of the data—taken from the National Health and Nutrition Examination Survey—that the researchers used. Respondents knew that their self-reports would accompany a medical examination, so they may have been more likely to honest about their heights and weights.
“Because of this, I believe our study underestimated the problem of under-reporting BMI,” she explains. “That said, other studies using different data have also reported that the under-reporting issue is not terribly huge to begin with and the correlations of self-reported BMI and measured BMI are typically pretty high.”
Also unexpected were the results involving income and education, Wen says.
“Another thing modestly surprising is that income is not linked to underreporting among men and only weakly among women,” she tells demodirt.com. “So if the difference effects between income and education indicate differential effects on social desirability, then this result might suggest education plays a bigger role in contributing to one’s social desirability of having an ideal body image than income.”
This conclusion, Wen adds, is speculation rather than evidence.
These results are most applicable, researchers say, when measuring the BMIs of different groups for health surveys and similar initiatives.
“The likelihood and extent of under-reporting BMI does vary across socio-demographic groups,” Wen concludes. “Some groups tend to more under-report BMI, such as white women. We need to be particularly careful when using self-reported BMI to study group differences.”
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