Tirzepatide vs Semaglutide Head-to-Head Systematic Review Across 10 Studies (Three RCTs, Seven Retrospective Cohorts) and 41,381 Adults Confirms 4.3 Percentage Points Greater Weight Loss With Tirzepatide Alongside Higher Serious Adverse Event Rate
A systematic review and meta-analysis of head-to-head comparisons of tirzepatide (Mounjaro/Zepbound) versus semaglutide (Ozempic/Wegovy) in adults with overweight or obesity — published in Diabetes, Obesity and Metabolism and covered by Medscape on September 9, 2026 with running weekend commentary — synthesized 10 studies (three randomized controlled trials and seven retrospective cohort studies) enrolling 41,381 adults. Tirzepatide produced a mean 4.28 percentage-point greater percent-body-weight reduction than semaglutide (10 studies) and a mean 4.43 kg greater absolute weight loss (8 studies). One head-to-head study reported average weight loss of 50.3 lbs (22.9 kg) on tirzepatide versus 33.1 lbs on semaglutide. Gastrointestinal adverse events were common in both arms but somewhat more frequent with tirzepatide; serious adverse event rates were rare but higher on tirzepatide than semaglutide. The pooled evidence supports the SURMOUNT-5 head-to-head randomized readout published in the New England Journal of Medicine in 2025 (Zepbound 20.2% vs Wegovy 13.7% weight loss at 72 weeks). The tirzepatide-semaglutide efficacy gap plus the safety trade-off remains a live clinical decision point in a market where 12%+ of U.S. adults are on the GLP-1 class per recent surveys.