Average Weight Loss in Clinical Trials
In the SURMOUNT-1 trial, adults with obesity or overweight (with comorbidities) on the highest dose of Zepbound (15 mg weekly) lost an average of 20.9% of body weight over 72 weeks, compared to 3.1% on placebo. For a 220-pound person, this equates to about 46 pounds.[1]
In SURMOUNT-2, patients with type 2 diabetes on 15 mg lost 14.9% on average (around 34 pounds for someone starting at 230 pounds), versus 3.4% on placebo.[1]
Who Achieved Maximum Weight Loss
About 30% of participants on 15 mg in SURMOUNT-1 hit 25% or more body weight loss—peaking near 25-30% for top responders after 72 weeks. Those with higher starting weights or better adherence saw the most.[1][2]
Maximum observed losses reached up to 57 pounds in some cases, but individual peaks varied by baseline BMI, diet, exercise, and duration.[3]
Factors Affecting Maximum Loss
Higher doses (10-15 mg) drive bigger losses than lower ones (e.g., 5 mg averaged 15% in trials). Combining with calorie restriction and 150+ minutes weekly exercise boosts results by 5-10% more. Losses plateau after 12-18 months, with many maintaining 20%+ long-term if continuing.[1][4]
Patients with BMI over 35 or no diabetes lose more on average than those with lower BMI or diabetes.[2]
Realistic Expectations Beyond Trials
Real-world data shows 15-25% loss over 1-2 years on 15 mg, though fewer reach 30% without strict lifestyle changes. Weight regain occurs if stopped—up to 2/3 of loss within a year.[4][5]
Weight Loss Timeline
| Weeks | Average % Loss on 15 mg (SURMOUNT-1) |
|-------|-------------------------------------|
| 20 | 15% |
| 40 | 18% |
| 72 | 21% |[1]
Compared to Wegovy or Mounjaro
Zepbound (tirzepatide) edges out Wegovy (semaglutide 2.4 mg), which averaged 15% loss in STEP trials—about 5-6% less. It matches Mounjaro (same drug, different branding) exactly.[1][6]
Who Might Hit the Upper End
Top responders: Women under 50, starting BMI 35-40, consistent dosing, and exercise. Men and older adults average 2-5% less.[2][3]
Sources
[1]: Zepbound Clinical Trials (FDA Label)
[2]: NEJM SURMOUNT-1 Results
[3]: SURMOUNT-1 Post-Hoc Analysis
[4]: Eli Lilly Real-World Data
[5]: JAMA Weight Regain Study
[6]: DrugPatentWatch: Tirzepatide Patents