Grade schools in Massachusetts are using so-called “fat letters” to alert parents when a child’s body mass index (BMI) and weight category reach an unhealthy status, but critics argue that the correspondence provides fuel for bullies, lowers self-esteem, and may spawn eating disorders.

A paper published today by the American Academy of Pediatrics addresses the concerns that parents may have with the policy, while highlighting why the messages could be an important tool for combating obesity in both children and adults. The public health agencies of 21 states have established or recommended mandatory assessment of height, weight, and body composition in public schools. Arkansas was the first to do so in 2003, but Massachusetts expanded upon this practice by having school nurses send confidential letters to homes that include advice on how to have discussions with healthcare providers in instances where a child is overweight or obese.

“Many critics have argued that BMI should not be used because of its misclassification of some muscular, athletic children,” wrote Dr. Michael R. Flaherty, a pediatric resident at Baystate Medical Center and Tufts University, in his discussion in the AAP’s journal Pediatrics. However Dr. Flaherty points out that BMI mislabels individuals in a very small percentage of cases. He maintains that the scale is a crucial tool in screening for obesity, although other measures are needed to make a definitive diagnosis. “Several studies have been conducted that have shown that childhood BMI, especially in the highest percentiles, correlates with adult obesity and the subsequent development of coronary artery disease,” Flaherty writes.

In Arkansas, where this policy was born, studies have shown that the negative consequences have been negligible, while more parents are signing kids up for sports. In addition, the "fat letters" have improved family diet and nutrition, suggesting a broad impact on the general population.

“Several of the most successful public health programs in children have been implemented using the public school system,” wrote Flaherty. “Mandatory school entrance vaccinations, dental examinations, and vision and hearing screening are just a few examples of successful initiatives aimed at keeping our children healthy and reducing problems early in their lives.”

Despite the positive results in Arkansas and elsewhere, some public health officials remain hesitant about the idea. Toronto schools are initiating their first investigation into measuring BMI in 12,000 pubic school students, but they opting out of sending "fat letters" for now.

“Our purpose is to identify the proportion of Toronto students who are a healthy weight, rather than to screen individuals for weight concerns,” wrote Dr. David McKeown, the city’s medical officer of health, to “We expect that by limiting the amount of information shared, we can minimize the risk of potential consequences associated with measurement such as weight-based bullying or teasing or unhealthy weight control practices.”

Source: Flaherty MR. “Fat Letters” in Public Schools: Public Health Versus Pride. Pediatrics. 2013.