As Longmonters gather around their Thanksgiving table for the annual feast of fats and carbs, , some medical experts are attacking an age-old gauge of obesity as obsolete and a major ingredient of “fat shaming” in our society.
The body mass index, or BMI, — which was developed by a Belgian mathematician nearly 200 years ago — should be retired as the default tool in society’s arsenal in the “war on obesity,” according to two leading critics of the BMI.
S. Bryn Austin, ScD, is professor of social and behavioral sciences at Harvard T.H. Chan School of Public Health and director of the “Strategic Training Initiative for the Prevention of Eating Disorders: A Public Health Incubator.”
Tracy K. Richmond, MD,MPH, is assistant professor of pediatrics at Harvard Medical School, and director of the Eating Disorders Outpatient Program at Boston Children’s Hospital.
They lay out their claims in an Oct. 19 editorial in the online MEDPAGETODAY website. Both slam the BMI as not accurate when it comes to diagnosing common viruses and misclassifies a large percentage of individuals as unhealthy when they are metabolically quite healthy.
“... A growing body of research on weight stigma in medicine has identified routine BMI assessment as a key barrier to care for people living in larger bodies and for others experiencing weight-based shame,” Austin and Richmond state.
The BMI is a person’s weight in kilograms (or pounds) divided by the square of height in meters (or feet), according to the Centers for Disease Control and Prevention. A high BMI can indicate high body fatness.
BMI screens for weight categories that may lead to health problems, the CDC says, but it does not diagnose the body fatness or health of an individual.
For adults 20 years old and older, someone with a BMI of 18.5 or below is considered underweight while anyone 25.0 to 29.9 is classified as overweight. A BMI of 30.0 or above is placed in the obese category, according to the CDC.
Dr. Antony Pearson, chief medical officer at Longmont United Hospital, said the BMI should not be shelved but continue to be used as a diagnostic tool to help shed light on potential health problems.
“A BMI is an estimate that is much like a Bell Curve and you can’t fit everything and everyone in a Bell Curve,” Pearson said. “There will always be outliers.”
Young athletes, who are heavy into weight lifting, are most likely to have a high BMI because they are muscular but not fat, he said.
However, a high BMI for most people is a sign that more work needs to be done on the health front, Pearson said.
“If you have a higher BMI your risk for certain diseases or even death is higher,” he said. “For example, if your BMI is over 40, then you are 20 times at higher risk of getting diabetes.”
Pearson said he once told a patient he had a high BMI and that prompted him to eat better and get more exercise. He dropped pounds and became much healthier.
“For him, it got him going down the right, healthier path,” Pearson said.
“I view the BMI as a good starting tool. You can use it to tell a patient ‘Here’s what you can do to modify your risks,’” Pearson said.
Austin and Richmond say even knowing they may be weighed at a doctor’s office may prompt some patients to delay medical care altogether, resulting in missed preventive care or worse.
“When patients do arrive to care, a focus on BMI can cause more problems than it resolves. Clinicians' focus on BMI can lead to unproductive weight-related conversations that fracture the doctor-patient relationship and may introduce mistrust.”
This can lead to patients ignoring physician advice, even when the advice is not focused on weight, the two say.
Even worse, the two say, misplaced BMI assessments can unnecessarily divert clinician focus to weight, an easy default but often misguided explanation for various signs and symptoms, and can result in missed diagnoses, sometimes with grave consequences.
“Thus, the BMI assessment may be causing risk … while providing minimal to no benefit,” the authors state.