Clinical trial results are impressive, but controlled trial environments differ from real life. Early real-world data is starting to emerge.
Clinical trial results (controlled)
- Wegovy: 14.9% average weight loss over 68 weeks (STEP-1)
- Mounjaro: ~21% average weight loss over 72 weeks (SURMOUNT-1)
Real-world factors that affect results
In the real world, results tend to be somewhat lower than clinical trials because:
- Adherence is lower — missed doses, delayed refills, cost barriers
- Less structured lifestyle support than trial environments
- Patients may have more complex health conditions than trial participants
- Some patients don't reach the maximum dose due to side effects
Early real-world data
Emerging Australian and international data suggests real-world weight loss averages roughly 10–15% for semaglutide and 15–18% for tirzepatide — lower than trials but still clinically significant.
The relative advantage of Mounjaro over Wegovy appears to hold in real-world settings, though the gap may be smaller than trial data suggests.
Full Wegovy vs Mounjaro comparison →
What drives the gap between trials and real life?
Several factors explain why real-world results are typically 3–5 percentage points lower than clinical trials:
- Adherence: In trials, participants are monitored closely and adherence is high. In real life, missed doses, delayed refills, and cost-driven interruptions are common. Even missing one dose per month reduces effectiveness.
- Dose tolerance: Some real-world patients don't reach the maximum dose due to side effects, choosing to stay at a lower, more comfortable dose. Trial protocols push toward maximum dose more aggressively.
- Lifestyle support: Trials include structured counselling on diet and exercise. Real-world patients may have less support, especially through pay-per-consult telehealth models.
- Patient selection: Trials exclude patients with certain conditions. Real-world patients often have more complex health profiles.
Does Mounjaro still beat Wegovy in real life?
Early evidence suggests yes — the relative advantage of tirzepatide over semaglutide appears to hold in real-world settings. Patients who switch from semaglutide to tirzepatide commonly report additional weight loss. The gap may be smaller than trial data suggests (perhaps 3–4% rather than 5–6%), but Mounjaro consistently outperforms.