For many the acronym BMI is not a misspelled nice foreign car, rather a threatening expression that they are overweight or obese. Yet while body mass index precisely classifies individuals along a range of above or below optimal weights as based on weight divided by the square of height, individual perception of “being heavy” varies quite a bit along ethnic lines.
Overweight black Americans are two to three times more likely than heavy white Americans to say they are of average weight – even after being diagnosed as overweight or obese by their doctors, according to a study led by Dana-Farber Cancer Institute researchers.
Weight “misperception” was most common among black men and women, and also was found among Hispanic men (but not women) compared to their white counterparts. The findings, which appear in the current online issue of the International Journal of Behavioral Nutrition and Physical Activity, are significant as excess body weight is a known risk factor for diabetes, heart disease, many forms of cancer, and premature death.
Growing concern over the national obesity epidemic in recent years apparently has not significantly increased overweight blacks’ recognition of their excess pounds, said Gary G. Bennett, PhD, of Dana-Farber’s Center for Community-Based Research and Harvard School of Public Health in Boston, lead author of the study.
The report by Bennett and Kathleen Y. Wolin, ScD of Northwestern University is based on an analysis of data collected in the National Health and Nutritional Examination Survey (NHANES), a government-sponsored research study begun in the 1960s. It includes both interviews and physical examinations carried out by mobile units across the country.
Analyses of NHANES data collected in 1988-98 and 2001-02 show that the prevalence of misperception actually has increased among blacks. “During this period we’ve seen rapid gains in obesity,” said Bennett. “We think it’s a considerable problem that this is still not resonating among blacks and other minorities,” he added.
Although the prevalence of overweight and obesity is even higher among blacks (estimated at over 75 percent) than the national average, Bennett said less pressure exists in the black community for people to lose weight through diet and exercise because of a cultural acceptance of higher body weights and heavier body shapes.
“We think that misperception can be very useful when it comes to protecting people against overly stringent body image ideals and eating disorders,” said Bennett, who is black. “But it’s a problem when people fail to realize the health consequences associated with obesity.”
The researchers analyzed data on 6,552 overweight and obese men and women who participated in the 1999-2002 NHANES surveys. Included in the analyses were data on height, weight, body mass index, whether they had received a diagnosis of overweight from a doctor, and responses to the question, “Do you consider yourself now to be overweight, underweight, or about the right weight”" Since all the participants were overweight or obese by standard health guidelines, all answers of “about the right weight” were categorized as “inaccurate” or a “misperception” by the researchers. The study was not designed to determine whether the inaccurate statements were intentional or not.
The study found that men were more likely than women to misperceive their weight. Among women, the prevalence of misperception was highest among overweight black women (40.9 percent, compared to 20.6 percent in overweight white women) and men (66.4 percent, compared to 43.2 percent in overweight white men). It was lowest among obese white women (3.1 percent, compared with 11.2 percent in obese black women) and men (8.9 percent, compared to 26.2 of obese black men.)
Altogether, overweight black men and women were twice as likely as whites to make inaccurate body weight perceptions, and obese black adults were even more likely to exhibit weight status misperceptions, according to the report.
Unrealistic assessments of body weight were just as common in people who were relatively financially well off as in poorer people, and in those who had been told by their doctors that they were overweight or obese.
One lesson from the findings, Bennett said, is that “it is probably not sufficient for physicians to simply tell a person that he or she is overweight; doctors should do much more intensive counseling regarding the health consequence of being overweight.”
The message is complicated, he added, by research findings showing that blacks generally don’t experience life-shortening health effects until they are more obese compared to whites. “Obesity-associated mortality occurs at a higher BMI (body mass index) among blacks than it does for whites,” probably for biological reasons, said Bennett. Yet some of the health effects associated with excess weight, such as diabetes, high cholesterol and hypertension, can be causing harm in blacks long before they result in death.
“The tendency to dramatically underestimate the degree of their overweight should be a clarion call to blacks,” Bennett said. “We hope that people will increasingly recognize the health consequences associated with excess weight.”