Who you calling fat?
BY KATE SILVER For Sun-Times Media October 2, 2013 5:20PM
Wondering what your BMI is? Find out by visiting 1.usa.gov/XBIO5L.
Updated: October 11, 2013 12:06PM
The subject of body mass index (BMI) is, undeniably, a weighty one.
While the body composition assessment has the power to label someone “normal” or “obese,” it has no way of determining whether that person actually is healthy. In fact, even those doing the measuring admit it’s an imperfect system.
“It’s not 100 percent,” says Dr. Rasa Kazlauskaite, an endocrinologist with Rush University Prevention Center at Rush University Medical Center.
BMI is derived based on a person’s body weight and height and assigned a number, which categorizes that person as underweight (below 18.5), normal (18.5-24.9), overweight (25-29.9) or obese (30 and above). When measuring adults, it doesn’t account for age, gender, ethnicity or muscle mass (kids’ tests do vary according to age and gender). In fact, it’s not uncommon for athletes, who have higher muscle mass, to fall into the “obese” category.
Still, because there are many health issues related to obesity, Kazlauskaite says that BMI is at least a good launching point. “Screening tools have to be cheap, simple with very, very low risk for the patients,” she says. If the reading causes concern, it’s a prompt for a patient to seek more exacting tests — and that’s a good thing, according to Kazlauskaite.
“In most instances, in probably about 70 percent of people, this body mass index measurement can be quite predictive of health,” she says. “But again, I do not think this should be the sole determination of how healthy people are.”
Don Disney echoes that sentiment. Disney is the director of youth initiatives with The Cooper Institute, developer of FitnessGram, the physical fitness testing and reporting method now used in the Presidential Youth Fitness Program, and has been adopted by 67,000 schools in all 50 states. (Several schools within Chicago Public Schools use FitnessGram, but CPS hasn’t adopted it systemwide). Body composition assessment is part of the program, along with testing aerobic capacity, flexibility, muscular strength and endurance. Participating schools give reports to kids and parents that indicate whether the child is in the “healthy fitness zone” or “needs improvement.”
FitnessGram offers three methods of body composition testing. BMI, says Disney, is the least accurate, but most widely used. Other methods are skin fold testing (aka calipers, or the “pinch” test) and bioelectrical impedance analysis (BIA), which sends a low-level electrical current through the body to determine composition. Because BMI can be calculated without touching kids or relying on other devices, it’s often the default method.
Disney emphasizes education is the most important testing element. Before students are tested, teachers are expected to explain what the tests mean and let them know that BMI assessments are not 100 percent accurate.
“I’ll be the first one to tell folks if they don’t educate and do the analysis, then don’t test the kids,” says Disney. “The students need to be empowered with understanding the tests, the limitations and all those factors prior to them getting the test.”
According to Daniel Le Grange, professor of psychiatry and behavioral neuroscience director with the Eating Disorders Program at The University of Chicago, it’s not just the kids that need to be educated. It’s also the parents.
Le Grange agrees it’s good for parents to know when their child’s measurements raise a red flag. He says that by screening children each year, a school nurse could detect eating disorders or other health issues early.
But, he emphasizes, if there is an issue with BMI, it should be communicated one-on-one between a school nurse, the parents and the child. It’s not something that should be sent home in a report.
“If the adolescent is upset because they’ve just been told that they’re very heavy, that’s the last thing they wanted to hear. That needs to happen in the presence of the parents, and the parents need to be counseled on how to manage that,” says Le Grange.
Kate Silver is a local freelance writer.