Background and Objective: Glucagon-like peptide-1 (GLP-1) receptor agonist therapy has intensified the policy debate over whether obesity pharmacotherapy increases short-term healthcare expenditures or reduces downstream medical costs (i.e., non-drug, acute-care expenditures). This study estimated same-year associations between GLP-1 use and medical spending among adults with observed obesity. Methods: Analyses used Medical Expenditure Panel Survey (MEPS) person-year files compiled from 2018 to 2022, with body mass index (BMI)-defined analyses restricted to 2019 and 2021. The primary analytic sample included 7144 person-years, of which 275 represented sustained GLP-1 users. Overlap-weighted Poisson pseudo-maximum likelihood models, utilization regressions, two-part decompositions, and a layered diagnostic framework were applied to assess spending patterns and same-year cost implications. Robustness was evaluated through sensitivity analyses across all-obesity, severe-obesity, and diabetes-excluded subsamples, as well as exploratory molecule-specific specifications. Results: Findings showed no evidence of same-year cost savings, but rather a distinct shift in spending composition. In fully adjusted primary models, GLP-1 use was associated with reduced non-drug medical spending (beta = -0.2494; marginal effect = -$2586 per person-year) and lower acute-care spending (beta = -0.5856; marginal effect = -$2019), while total medical spending was higher (beta = 0.3182; marginal effect = +$6483). Point E values of 1.89 (non-drug) and 2.99 (acute-care) indicated moderate-to-strong resilience to unmeasured confounding. Negative control models using dental spending and visits showed significant positive associations. Since this residual confounding operates in the direction opposite to the negative acute-care association, the headline compositional pattern is unlikely to be an artifact of upward health-seeking bias. Utilization models indicated fewer inpatient discharges (IRR = 0.686) and inpatient nights (IRR = 0.524). Two-part models further suggested that the reduction in acute-care spending was concentrated on the intensive margin among individuals with positive expenditures. Conclusions: The use of GLP-1 is not associated with overall short-term cost savings. This usage is related to a shift in the composition of observed medical spending during the same year. This change is leading to a decline in hospital admissions and acute care costs, in parallel with the rise in pharmaceutical spending. Non-drug and acute-care costs were lower among regular users. However, total spending was at a higher level, consistent with a trend in the budget records from that period in which drug costs were the dominant factor. These associations are consistent with a potential reallocation of healthcare resources from inpatient acute care toward pharmacy and ambulatory services, with corresponding planning implications for payers and possible workforce reallocation of nursing capacity from acute to outpatient settings, contingent on replication in post-2022 data.
GLP-1 Therapies