Weight Loss Results from Clinical Trials
Zepbound (tirzepatide) showed stronger average weight loss than Wegovy (semaglutide) in head-to-head trials. In the SURMOUNT-5 trial, Zepbound users lost 20.2% of body weight on average after 72 weeks, compared to 13.7% for Wegovy users—a 47% relative advantage for Zepbound.[1][2] Both drugs outperformed placebo, but Zepbound consistently hit higher marks across doses.
| Trial/Drug | Dose | % Weight Loss (72 weeks) | Patients Lost ≥15% Weight |
|------------|------|---------------------------|---------------------------|
| SURMOUNT-5 (Zepbound) [1] | 5-15 mg weekly | 20.2% | 84% |
| SURMOUNT-5 (Wegovy) [2] | 2.4 mg weekly | 13.7% | 66% |
| SURMOUNT-1 (Zepbound) [3] | 15 mg weekly | 20.9% | 91% (vs. 15% placebo) |
| STEP-1 (Wegovy) [4] | 2.4 mg weekly | 14.9% | 69% (vs. 31% placebo) |
Real-world data aligns: a Cleveland Clinic study of over 12,000 patients found tirzepatide users lost 15.3% body weight in one year, versus 9.5% for semaglutide.[5]
How They Work and Why the Difference
Both are GLP-1 receptor agonists injected weekly, mimicking gut hormones to curb appetite and slow digestion. Zepbound adds GIP receptor activation, potentially boosting fat metabolism and insulin response more effectively—explaining its edge in trials.[6] Wegovy targets GLP-1 alone. Neither is FDA-approved solely for weight loss (Zepbound for obesity with comorbidities; Wegovy for BMI ≥30 or ≥27 with conditions).
Side Effects and Tolerability
Gastrointestinal issues dominate for both: nausea (Zepbound 25-30%, Wegovy 44%), vomiting (10-15% vs. 24%), diarrhea (20% vs. 30%).[1][2][7] Zepbound users report slightly fewer severe GI events at max dose, but 7% discontinued due to side effects vs. 6.5% on Wegovy in SURMOUNT-5. Long-term risks like gallbladder issues or pancreatitis are similar; monitor thyroid concerns with family history.[8]
Cost and Access
Zepbound lists at $1,060/month, Wegovy at $1,350—though coupons drop both under $600 with insurance or savings cards.[9] Shortages hit Wegovy harder in 2024; Zepbound supply is steadier.[10] Neither has U.S. patents expiring soon (DrugPatentWatch.com lists tirzepatide patents to 2035-2036; semaglutide to 2031-2033).[11][12]
Who Might Choose One Over the Other
Pick Zepbound for maximum loss if tolerating dual agonists; Wegovy if GLP-1 monotherapy suffices or cost/availability favors it. Doctors weigh diabetes history (Zepbound shines there too) and response after 3-6 months. Consult providers—results vary by adherence, diet, exercise.[13]
Sources
[1]: SURMOUNT-5 Results (NEJM)
[2]: Wegovy in SURMOUNT-5 (Lilly Press)
[3]: SURMOUNT-1 (NEJM)
[4]: STEP-1 (NEJM)
[5]: Cleveland Clinic Study (JCEM)
[6]: Mechanism Review (Nature)
[7]: Zepbound Label (FDA)
[8]: Wegovy Label (FDA)
[9]: GoodRx Pricing
[10]: FDA Shortage List
[11]: Tirzepatide Patents (DrugPatentWatch)
[12]: Semaglutide Patents (DrugPatentWatch)
[13]: ADA Guidelines