A systematic review and meta-analysis conducted by Oxford University researchers and published in The BMJ (DOI: 10.1136/bmj-2025-085304) provides sobering evidence about the durability of weight loss achieved through medications like semaglutide and tirzepatide — the GLP-1 receptor agonists marketed as Ozempic, Wegovy, Mounjaro, and Zepbound.
The research team, led by Sam West, Jadine Scragg, Paul Aveyard, and Jason L Oke, pooled data from 37 clinical trials and observational studies encompassing 9,341 participants. The average treatment duration was 39 weeks (approximately 9 months), with an average follow-up period after cessation of 32 weeks (approximately 8 months).
The primary finding: across all medications studied, post-cessation weight regain averaged 0.4 kg per month. For the newer GLP-1 medications specifically, regain was approximately double — 0.8 kg per month — with a projected return to pre-treatment weight within 1.5 years. The researchers also found that all measured cardiometabolic improvements (HbA1c, fasting glucose, blood pressure, cholesterol, triglycerides) were projected to return to baseline within 1.4 years, suggesting the health benefits are contingent on continued medication use.
The comparison to behavioral weight management is the study's most headline-generating finding: medication-related weight regain was nearly four times faster than regain after ending diet and exercise programs. However, this comparison merits careful scrutiny. It was derived from a cross-study comparison, not a head-to-head trial. The medication and behavioral intervention populations were drawn from entirely separate studies, meaning differences in participant characteristics — obesity severity, motivation, socioeconomic status, comorbidities, access to support systems — could confound the comparison.
Several additional limitations deserve attention. Only 8 of 37 included studies examined the newer GLP-1 medications, and none tracked participants beyond 12 months post-cessation. The projected timelines (1.5-1.7 years to baseline) are therefore mathematical extrapolations from shorter-term observed data, not actual observed outcomes. The assumption of linear regain implicit in these projections may not hold — weight regain could decelerate, plateau, or accelerate over time.
The study's treatment of medication discontinuation as a homogeneous event also obscures important heterogeneity. Reasons for stopping include adverse side effects, prohibitive costs (often $1,000+ per month without insurance), insurance coverage changes, or personal choice. These different pathways to discontinuation may be associated with different baseline characteristics and different post-cessation behaviors, potentially confounding the average regain rate.