Quick Answer
Based on clinical trial data, Mounjaro (tirzepatide) has shown the greatest average weight loss at 22.5% of body weight over 72 weeks (SURMOUNT-1 trial, NEJM 2022). Wegovy showed 14.9% over 68 weeks, while Saxenda showed 8.0% over 56 weeks.
Detailed Answer
Based on the highest-quality clinical trial evidence available, Mounjaro (tirzepatide) has demonstrated the greatest average weight loss of any currently available weight loss medication in the UK. In the landmark SURMOUNT-1 trial published in the New England Journal of Medicine in 2022, participants taking the highest dose (15mg) lost an average of 22.5% of their body weight over 72 weeks.
For comparison, Wegovy (semaglutide 2.4mg) showed an average weight loss of 14.9% over 68 weeks in the STEP 1 trial (also published in NEJM), while Saxenda (liraglutide 3.0mg) showed approximately 8.0% over 56 weeks in the SCALE trial.
However, these are average results from large clinical trials. Individual responses vary significantly — some patients lose more weight than the average, while others lose less. Factors such as adherence to dietary and lifestyle changes, individual metabolism, starting weight, and comorbidities all influence outcomes.
It is also important to note that direct head-to-head comparisons between all three medications are limited. The SURMOUNT-3 and SURMOUNT-4 trials provide additional data for tirzepatide, and the STEP programme extends to multiple studies for semaglutide. Cross-trial comparisons have inherent limitations due to different patient populations and study designs.
Your prescriber will recommend the most appropriate medication based on your individual clinical profile, not just headline efficacy figures.