Real-World Body Composition and Blood Pressure Changes Following Glucagon-Like Peptide 1 Receptor Agonist Initiation:...

To characterize real-world body composition and blood pressure changes following glucagon-like peptide (GLP)-1 receptor agonist (RA) initiation and identify predictors of weight loss quality using connected device data.

In this retrospective cohort study, adult US users completing an in-application GLP-1 RA survey (June 8, 2023, to July 4, 2024) were followed up using longitudinal device data (December 2021 to September 2025). We used a distributional causal inference framework to match GLP-1 RA users to nonusers. Primary estimands were the distributional average treatment effect on the treated and median differences over months 10 to 14.

Among 2031 users for body composition (396 exposed) and 672 for blood pressure (BP; 148 exposed), GLP-1 RA initiation was associated with a 9.8% median weight reduction (95% CI, 9.8-9.9), driven by fat mass loss (7.5%; 95% CI, 7.5-7.8) with smaller muscle mass loss (2.3%; 95% CI, 2.1-2.4). Sustained reductions were observed in systolic (2.5 mm Hg; 95% CI, 1.5-2.9) and diastolic BP (1.5 mm Hg; 95% CI, 1.2-1.9). Baseline muscle-to-fat ratio (MFR) was the strongest predictor of weight loss quality, with lower MFR individuals losing more fat and sparing more muscle.

In a real-world setting, GLP-1 RA initiation was associated with clinically significant fat-predominant weight loss and sustained BP improvements. Baseline MFR predicted weight loss quality, suggesting that pretreatment body composition may help clinicians anticipate individual responses-a step toward precision medicine in GLP-1 RA therapy.