NEJM Tirzepatide Study: SURMOUNT Trial Results Explained
Complete breakdown of the NEJM tirzepatide SURMOUNT trial results — what the data shows about weight loss of up to 22.5%, side effects, and how it compares to semaglutide.
Written by Trimi Medical Team. Medically reviewed by Dr. Amanda Foster, MD. This article interprets published clinical trial data for patient education.
Quick links: Semaglutide treatment, tirzepatide treatment, and SURMOUNT trials explained.
More on GLP-1 Clinical Evidence
Tirzepatide: The Next Generation of GLP-1 Therapy
If semaglutide was the breakthrough that changed obesity medicine, tirzepatide is the next evolution. Published in the New England Journal of Medicine in July 2022, the SURMOUNT-1 trial demonstrated weight loss results that exceeded anything previously seen with any non-surgical intervention. At the highest dose, participants lost an average of 22.5% of their body weight — approaching the range of weight loss typically associated with bariatric surgery.
Tirzepatide works differently from semaglutide. While semaglutide activates only the GLP-1 receptor, tirzepatide is a dual agonist that activates both the GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. This dual mechanism of action is believed to contribute to its superior weight loss efficacy, though the exact contribution of each pathway is still being studied.
The SURMOUNT-1 trial enrolled 2,539 adults with obesity (BMI 30 or higher) or overweight (BMI 27 or higher) with at least one weight-related comorbidity. Participants were randomized to receive tirzepatide at 5 mg, 10 mg, or 15 mg weekly, or placebo, all alongside lifestyle intervention. The results across all three dose levels were remarkable — and the data has important implications for patients considering tirzepatide treatment.
SURMOUNT-1 Key Results
| Metric | 5 mg | 10 mg | 15 mg | Placebo |
|---|---|---|---|---|
| Avg. Weight Loss | 15.0% | 19.5% | 22.5% | 3.1% |
| Lost 5%+ | 85% | 89% | 91% | 35% |
| Lost 10%+ | 69% | 78% | 84% | 14% |
| Lost 20%+ | 35% | 46% | 57% | 3% |
| Nausea Rate | 24% | 33% | 31% | 10% |
| Discontinuation | 4.3% | 7.1% | 6.2% | 2.6% |
What Makes Tirzepatide Different
The dual GIP/GLP-1 mechanism sets tirzepatide apart from single-target GLP-1 medications. GIP receptor activation appears to enhance the metabolic effects of GLP-1 signaling, potentially improving insulin sensitivity, fat metabolism, and appetite regulation through complementary pathways. This dual approach may explain the superior weight loss seen in the SURMOUNT trials compared to the STEP trials with semaglutide.
Interestingly, the side effect profile is similar to or slightly better than semaglutide, despite the greater weight loss. Nausea rates at the highest tirzepatide dose (31%) were lower than what was observed with semaglutide 2.4 mg in the STEP 1 trial (44%). This suggests that the GIP component may actually mitigate some of the gastrointestinal effects typically associated with GLP-1 receptor activation.
Semaglutide vs Tirzepatide: The Data Side by Side
| Comparison | Semaglutide 2.4mg | Tirzepatide 15mg |
|---|---|---|
| Avg. Weight Loss | 14.9% | 22.5% |
| Lost 20%+ | 32% | 57% |
| Mechanism | GLP-1 only | GIP + GLP-1 dual |
| Nausea Rate | 44% | 31% |
| Study Duration | 68 weeks | 72 weeks |
| FDA Approved | Yes (Wegovy) | Yes (Zepbound) |
| Long-term Data | More extensive | Growing |
Comparison Caveat
These results come from separate trials with different patient populations, not head-to-head comparisons. Direct comparison should be interpreted cautiously.
Accessing Tirzepatide Treatment
Brand-name tirzepatide for weight loss (Zepbound) carries a list price of approximately $1,000 per month without insurance. Compounded versions are available through telehealth providers at significantly lower cost. Trimi offers both compounded semaglutide and tirzepatide, allowing providers to recommend the medication best suited to each patient's individual profile and goals.
Whether semaglutide or tirzepatide is right for you depends on multiple factors including your health history, treatment goals, tolerability preferences, and budget. A qualified metabolic health provider can help you weigh these factors based on the clinical evidence from both the STEP and SURMOUNT trials.
Bottom Line
The NEJM tirzepatide data establishes it as the most effective non-surgical weight loss medication studied to date. With average weight loss of 22.5% at the highest dose and a favorable side effect profile, tirzepatide represents a significant advancement over existing treatments. The evidence supports tirzepatide as a powerful option for patients who want maximum weight loss potential. Trimi makes both semaglutide and tirzepatide accessible through specialized providers at transparent pricing, so patients can make evidence-based treatment choices with their provider.
Frequently Asked Questions
What did the NEJM tirzepatide study find?
The SURMOUNT-1 trial published in the NEJM found that tirzepatide at the highest dose (15 mg) produced average weight loss of 22.5% of body weight over 72 weeks. Even the lowest dose (5 mg) produced 15% weight loss. These results exceeded those seen with semaglutide in the STEP trials, making tirzepatide the most effective non-surgical weight loss medication studied to date.
How does tirzepatide compare to semaglutide?
In clinical trials, tirzepatide at the highest dose produced approximately 22.5% weight loss versus semaglutide's 14.9% at its highest dose. Tirzepatide works through a dual mechanism (GIP and GLP-1 receptors) compared to semaglutide's single GLP-1 mechanism. However, direct head-to-head comparison trials are limited, and individual responses vary.
What were the side effects of tirzepatide?
Similar to semaglutide, the most common side effects were gastrointestinal — nausea, diarrhea, vomiting, and constipation. These occurred at similar or slightly lower rates than semaglutide in separate trials. Most side effects were mild to moderate and decreased over time as the body adjusted to the medication.
Is tirzepatide safe for weight loss?
Tirzepatide received FDA approval for weight loss (as Zepbound) in November 2023, based on the safety and efficacy data from the SURMOUNT trials. The safety profile is similar to other GLP-1 medications. Long-term safety data continues to be collected. The medication is contraindicated in patients with certain thyroid conditions and a history of pancreatitis.
How long does it take tirzepatide to work?
Weight loss typically begins within the first few weeks but becomes more pronounced as the dose is titrated up over 3 to 5 months. In the SURMOUNT-1 trial, weight loss continued throughout the 72-week study period, with the most rapid loss occurring during the first 6 months at full dose.
Can I get tirzepatide through telehealth?
Yes, several telehealth providers offer compounded tirzepatide. Trimi offers both compounded semaglutide and tirzepatide, with providers who can help determine which medication is best suited to your individual health profile. Brand-name Zepbound requires insurance coverage for affordable access.
Will tirzepatide replace semaglutide?
Both medications have their place. Tirzepatide shows greater average weight loss in clinical trials, but semaglutide has more long-term safety data and a larger evidence base. Some patients respond better to one than the other. Having both options available allows providers to personalize treatment based on individual response and tolerability.
Sources & References
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205-216.
- Wilding JPH, et al. STEP 1 trial. N Engl J Med. 2021.
- Zepbound (tirzepatide) FDA prescribing information.
- Wegovy (semaglutide) FDA prescribing information.
- FDA approval announcement for Zepbound.
- NIDDK prescription weight loss medications.
- WHO obesity fact sheet.
- CDC obesity statistics.
Medical Disclaimer: This content is for educational purposes only and does not constitute medical advice. Clinical trial results represent averages and individual outcomes will vary. Always consult a qualified healthcare provider before starting any medication. Trimi offers tirzepatide treatment — readers should be aware of our perspective.