Exploring BMI Classification Changes and Disparities Upon Incarceration in U.S. Federal Prisons

Information on body mass index (BMI) fluctuations during multiyear incarceration is limited, with publications on BMI changes leading to reclassification even more sparse. This is particularly important because access to novel treatments, such as glucagon-like peptide-1 (GLP-1) therapies, in the United States depends on BMI classification rather than the exact BMI value. This retrospective analysis explores BMI classification changes over 2 years to assist public health interventions. The dataset included 30,693 individuals with at least two recorded height and weight measurements, accounting for 31, 299 incarcerations between January 1, 2018, and December 31, 2021 across 37 U.S. federal prisons. BMI classification changes were tracked and categorized as upward, downward, or unchanged using the Centers for Disease Control and Prevention BMI classification system. The analysis included descriptive statistics by age group, sex, race, ethnicity, and education, as well as adjusted logistic regression models. One-third of individuals experienced BMI classification changes. Females and individuals without a verified high school diploma/GED who were not participating in the GED program had 20% and 37%, respectively, higher odds of upward reclassification. These findings suggest the need for interventions tailored to address BMI classification changes upon incarceration to meet individual needs.