Maybe BMI Report Cards Weren’t the Best Idea

This article was originally published by Undark Magazine.

Among Lexie Manion’s memories of her junior year of high school in New Jersey was the experience of being regularly hassled by a school nurse who was trying to weigh her.

The nurse, Manion recalled, was trying to get Manion’s weight on file—a common practice at schools across the United States, which aim to use the data to improve student health. But for Manion, who had an eating disorder, the experience was deeply distressing. The thought of getting on a scale in school—of someone other than her doctor handling this sensitive measurement—terrified Manion. It also triggered her eating disorder: She began to restrict her food intake more intensely to lose weight before the school nurse put her on a scale.

“I was worried about her knowing my weight, and I was worried the whole school would somehow know the number if she weighed me,” Manion, now 29, wrote in an email to Undark. “I became very anxious and would avoid the scale and her gaze every time she inquired.”

The policy at Manion’s school was part of a national effort to combat childhood obesity by collecting—and often sharing—data on students’ weight. Starting in 2003, one study found, 29 states enacted policies encouraging or requiring school districts to weigh students, or to go further and calculate their body-mass index, or BMI: a common tool for categorizing people based on their weight and height. By the policy’s peak extent, in the 2010s, millions of students each year were receiving so-called “BMI report cards” in the mail—and some students even saw their weight status appear on their actual report cards, alongside their grades. Policy makers hoped that by telling students and their family about a child’s weight category, the reports would prompt them to make healthier choices and lose weight, reducing childhood obesity one student at a time.

But even as the practice was becoming more common, research was already suggesting that BMI screenings have no impact on students’ weight and can even cause harm. Today, many experts say, the evidence is clear that school BMI screenings do little to improve student health. Research has also linked the policy to increased weight-based bullying and body-image dissatisfaction, which, as in Manion’s experience, can trigger or worsen eating disorders. In response, some states, including California, have stopped requiring screenings.

Nevertheless, BMI screening or similar policies that mandate or encourage weight-tracking remain on the books in at least 16 states, including Tennessee, West Virginia, Arkansas, and New York, according to Undark’s review of state legislative codes.

“To focus efforts on just measuring the increasing waistline of America is a Band-Aid,” says Kristine Madsen, a pediatrician and a public-health nutrition researcher at UC Berkeley, who conducted one of the largest studies of school BMI screenings to date. “It doesn’t even touch the underlying problem, and it’s ineffective.”

Arkansas was the first state in the nation to mandate screening and reporting, back in 2003. Then, in 2005, the Institute of Medicine at the National Academy of Sciences released a 434-page report, “Preventing Childhood Obesity: Health in the Balance,” that urged more states to adopt the practice. “It is important for parents to have information about their child’s BMI and other weight-status and physical fitness measures, just as they need information about other health or academic matters,” the NAS group wrote.

The group was responding to what it described as a childhood-obesity epidemic. At the time, about one-third of U.S. children were classed as overweight, obese, or severely obese. Childhood obesity is linked to a range of poor health outcomes, including high blood pressure, asthma, and heart disease.

More states moved to implement BMI screening. By 2010, just five years after the NAS’s recommendation was published, 29 states were widely conducting some form of body assessment on their students, according to an academic survey of state education departments.

Those policies typically offered little guidance on how the weigh-ins should be conducted. According to one study, about half of screenings were done during gym class, often in front of other students. The gym teacher or school nurse would measure each student’s height and weight and submit them to the school, which, in many cases, would pass the data along to state health authorities for population-level tracking.

Baked into that model from the start, some experts say, were problems. Foremost among them was, in many policies, the reliance on BMI.

The 1832 paper that first proposed the metric, and the 1972 study that sparked its modern usage, involved only men and weren’t representative of the ethnic and racial diversity of the United States. BMI also doesn’t consider factors such as muscle mass. “This was intended to describe large groups of people; it was not intended to be an individual litmus test for health,” says Leah Graves, a registered dietitian who specializes in treating eating disorders. Graves and others question whether BMI offers families useful information about students’ overall health.

The school policies soon ran into another problem: There wasn’t much evidence that they worked.

Not long after the NAS recommendation was released, scientists began publishing studies on school weigh-ins. In 2009, for instance, two pediatrics experts published a review of the existing research, finding that there was no impact on students’ weight. Parents, they wrote, didn’t seem to be learning much from BMI report cards, and there didn’t seem to be any increase in healthy behaviors at home.

In 2014, Madsen, the UC Berkeley researcher, and several of her colleagues launched a randomized clinical trial. The researchers took nearly 29,000 students in California public elementary and middle schools and split them into three groups. One group didn’t get screened at all. The second was screened, but participants never found out the results. A third group received screenings, and the participants’ caregivers were sent BMI report cards. The researchers followed the group from 2014 to 2017 to track changes in weight and adverse outcomes.

The team’s results, published in 2021, showed that neither screening nor reporting had an impact on weight change over the years. Additionally, the two groups that were screened reported more weight dissatisfaction and peer weight talk than the group that wasn’t screened.

Madsen’s research has also found that the experience can be upsetting for students. In one 2022 survey of more than 11,000 students in California, her team found that 49 percent were weighed by gym teachers, as opposed to just 28 percent who were weighed by school nurses; the students were more likely to feel less comfortable being weighed by a teacher than by a nurse, and were more likely to feel that they lacked privacy while being weighed.

Other research has documented the potential for long-term harms from that experience. The negative effects of adolescents perceiving themselves as overweight can last for years into adulthood, long after the screenings have ended, according to one 2023 survey. Although the study didn’t specifically ask about BMI screening, it linked a perceived overweight status to increased self-starvation, bingeing, purging, and overexercising, as well as the development of eating disorders.

Not every expert is convinced that BMI screening for the sake of data collection is necessarily harmful. Researchers and school professionals say that it’s the way these screenings are conducted that can cause problems. As a result, some professional organizations and government agencies have issued guidelines intended to improve the experience.

The Centers for Disease Control and Prevention, which has no formal position on BMI screenings, has a public set of 10 safeguards schools can implement to address concerns about screenings. The list includes recommendations such as measuring students’ height and weight in a private place, having nurses instead of teachers take the measurements, and asking for parental consent before measuring students.

But a 2019 CDC survey of more than 200 schools found that these safeguards had not been widely implemented. Only 3 percent of the schools had at least four of the safeguards in place, and 19 percent had no safeguards at all.

“These safeguards came out kind of pragmatically, recognizing that there’s not enough evidence at that point to say whether or not BMI-measuring schools is definitively harmful or helpful, but schools are doing it,” says the CDC school-health researcher Sarah Sliwa. “So, if they’re doing it, what are some steps they can take to try to minimize those harms and increase the likelihood that data are collected in a way that’s transparent and useful?”

As the school staff members who are most often asked to weigh students, physical educators have also developed standards regarding body measurement in schools.

The Society of Health and Physical Educators, or SHAPE America, a professional organization, has a formal statement on fitness testing—which can include BMI screenings, among other assessments—that states that the organization finds the testing valuable only when it’s integrated appropriately into the curriculum, and when the results aren’t used to grade students. SHAPE America recommends that schools first teach students about the fitness testing and why it’s done, as well as prepare them for the process and help them set personalized goals based on the outcome of the testing. But the organization does not have an official recommendation on whether to conduct BMI screenings.

“There’s a lot of body stigma, and we have other data points that we can use without having students feel that they’re being judged,” says Cara Grant, the president of SHAPE America.

The American School Health Association, an organization of school nurses and other health professionals, also does not have an official position on BMI screenings, says Kayce Solari Williams, ASHA’s former president.

In order to effectively realize the CDC guidelines, Sliwa says, schools need to implement safeguards or best practices. Because of a lack of the funding and staffing, though, they often fail to do so.

Some states have responded to the research showing harms from BMI screenings. In 2013, Massachusetts struck BMI reporting from its schools but maintained a screening requirement. Illinois made BMI screening optional for its students in 2015. California eliminated screening and reporting requirements from its annual fitness testing. In New York, schools still screen for BMI, but they are no longer required to send BMI report cards home.

Other states have not made changes. In Georgia, screening and reporting are required by law. In West Virginia, which has some of the highest levels of childhood obesity in the country, state law requires the collection of BMI data to be reported to the Department of Education, the governor, the State Board of Education, the Healthy Lifestyles Coalition, and the Legislative Oversight Commission on Health and Human Resources Accountability.

In New Jersey, where Manion attended high school, BMI screening is not mandated, but it’s allowed on a district-by-district basis. The state does require weight measurement, however.

“What’s the value?” asks Madsen, the UC Berkeley researcher. She questions whether the policies are a good use of school resources. “The entire point of sending them home is actually to support families in creating healthier lifestyles,” she says. “But they’re not.”

Amanda Salazar is a freelance journalist from Brooklyn, New York.