It’s been three years, and CBS’s Thalia Assuras still hasn’t done her biology homework on the limitations of the body mass index (BMI).
In a weekend “Evening News” story on a new university study that grades states with an A-F scale on the prevalence of childhood obesity, the reporter failed to tell viewers of the limitations of the weight index for medical evaluation – something she neglected to do in a similar story in 2004.
“In its third report card on state efforts to control their children’s weight, The University of Baltimore [1] gave six states an ‘A.’ New Jersey, which we visited three years ago, managed a ‘B.’ So we returned to take another look,” anchor Thalia Assuras told viewers of the January 27 “Evening News” as she introduced her taped report.
Assuras failed to tell viewers that no medical professional is listed among the researchers who authored the study. In fact, the study was written by a professor of economics, a professor of finance, a Ph.D. in public administration, and the assistant director [2] for the school’s Schaefer Center for Public Policy, who previously served as a ”senior enforcement attorney at the U.S. Office of the Comptroller of the Currency.”
Opening her videotaped story, Assuras revisited a Garden State school she had featured on the Jan. 24, 2004, “Evening News” and talked with school nurse Noreen Scully, whom she also featured three years ago.
While Assuras noted that school nurse Scully has “seen a positive trend” among the children she’s surveyed in the past three years, the CBS weekend anchor warned her audience over footage of pudgy kids in a school cafeteria that “most of America’s children are still losing the battle of the bulge.”
In fact, “the obesity rate in children and teenagers is up from 16 to 17.1 percent” and “could rise to 20 percent at the end of the decade,” Assuras complained, citing an Institute of Medicine study.
But in the midst of alarming her audience, Assuras failed to inform them of the limitations of the body mass index, which researchers have known for at least 19 years.
“The use of BMI is not bad or wrong,” but it “carries considerably less scientific information than does reliably measured body density or full sets of skinfold, bodycircumference, and bone-breadth measurements,” Drs. Marc S. Micozzi of the Armed Forces Institute of Pathology and Demetrius Albanes of the National Cancer Institute noted in a letter to the editor of the September 1988 American Journal of Clinical Nutrition (AJCN) [3].
“The interpretation by epidemiologists of BMI as a pure measure of fatness is incorrect. Otherwise, the BMI, like any other tool, remains useful in populations as long as its use is appropriate to the goals of a study, its characteristics are understood, and its limitations are clearly stated,” Micozzi and Albanes concluded.
Ten years later, the government instantly designated millions of Americans “overweight” by changing the BMI guidelines to conform with those observed by the World Health Organization, another caveat left unmentioned by Assuras in both her 2004 and 2007 reports.
And while the government’s measure of obesity has changed since Micozzi and Albanes wrote of their concerns in 1988, nutrition experts still caution it’s merely one tool in research and should not be taken as a substitute for a personal medical evaluation.
Indeed, a healthy BMI number can lend the wrong impression about a child’s overall nutritional health.
“An explosion of ‘super-sized’ kids has American health professionals greeting the body mass index (BMI) with open arms. But preliminary findings from a large-scale CNRC study suggest tempering enthusiasm with an understanding of the BMI's limitations,” noted a Summer 2000 article at kidsnutrition.org, a Web site for Baylor University’s Children’s Nutrition Research Center (CRNC). [4]
“One out of six children whose BMI value was in the normal range was found to have an unhealthy level of body fat. And one out of four with a BMI in the at-risk to obese range actually had a body-fat percentage in the normal range,” said Baylor University professor of pediatrics Dr. Kenneth Ellis.
“Clearly, if we rely solely on the BMI, kids who probably need some type of intervention could fall through the cracks,” Ellis concluded.
Assuras failed to mention those concerns, and she didn’t give air time to education officials from states that refuse to track BMI in their students, such as Texas or Georgia.
The Business & Media Institute has previously criticized the media for its frequent, uncritical, and sometimes inaccurate use of BMI. The Dec. 14, 2004, study, “SuperSized Bias II,” [5] for example, noted that “The major media couldn’t keep straight how many children are overweight, according to the CDC (16 percent currently). The numbers varied wildly, sometimes even in the same news outlet.”