BMI Reporting and Accuracy of Child's Weight Perception.

Objectives: To estimate whether school-based body mass index (BMI) reports impacted the accuracy of children's self-reported weight category, for children overall and within subgroups.

Methods: We analyzed existing data from the Fit Study, a randomized controlled trial of a BMI screening and reporting intervention conducted in California from 2014 to 2017. The sample included 4690 children in 27 schools randomized to receive BMI reports and 4975 children in 27 controls schools that received BMI screening only. To estimate how BMI reporting affected accuracy, we fit multinomial logistic regression models to our data. We calculated average marginal effects, which capture the change in probability that children more accurately reported their weight category because of BMI reporting.

Results: We detected no impact of BMI reporting on children's self-reported weight accuracy. Exploratory subgroup analyses show that for Black children, exposure to 1 round of BMI reporting was associated with a 10.0 percentage point increase in the probability of accurately reporting their weight category (95% confidence interval [CI]: 2.6 to 17.4). Two rounds of reporting were associated with an increase in the probability of accuracy for Asian children (6.6 percentage points; 95% CI: 0.4 to 12.8), 5th graders (11.1 percentage points; 95% CI: 1.6 to 20.5), and those with BMI <5th percentile (17.1 percentage points; 95% CI: 2.7 to 31.6).

Conclusions: BMI reporting has limited efficacy in increasing children's weight perception accuracy. Although exploratory analyses show that specific subpopulations became more accurate, future prospective studies should be designed to confirm these results.