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Tirzepatide at maximum tolerated dose achieved 21.9% bodyweight reduction over 112 weeksTrial shows tirzepatide helps maintain weight loss over two years

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Key Takeaway
Consider tirzepatide at MTD for sustained weight loss; a 5 mg dose provides an alternative if MTD is poorly tolerated.

This Phase 3b randomized controlled trial was conducted in a multicentre setting in the USA to evaluate the efficacy and safety of tirzepatide in adults with obesity. The study population included adults aged 18 years or older with a body mass index (BMI) of 30 kg/m2 or greater, or a BMI of 27 kg/m2 or greater with at least one weight-related comorbidity. A total of 441 participants were enrolled, with 378 successfully randomized into three groups: tirzepatide at the maximum tolerated dose (MTD), tirzepatide 5 mg, and a placebo group.

The study design included a 60-week open-label weight-loss period followed by a 52-week double-blind maintenance period, totaling 112 weeks of follow-up. The primary outcome was the percentage change in bodyweight from baseline to week 112. Tirzepatide at MTD (n=140) resulted in a -21.9% weight reduction (95% CI -23.5 to -20.3). The tirzepatide 5 mg group (n=144) showed a -16.6% reduction (95% CI -18.0 to -15.1), while the placebo group (n=94) showed a -9.9% reduction (95% CI -11.1 to -8.8). The p-value for these differences was less than 0.0001.

Secondary outcomes focused on safety and tolerability. Gastrointestinal events were the primary reported adverse events. These events were characterized as mild to moderate in severity and predominantly occurred during the dose escalation phase of the trial. No specific data regarding serious adverse events or discontinuation rates were reported. The study noted that while tirzepatide at MTD maintained significant weight reduction, individual treatment responses may vary when the dosage is reduced to 5 mg.

These results align with previous findings indicating that tirzepatide at maximum tolerated dose leads to significant weight reduction in patients with obesity. The trial confirms that maintaining a high dose of tirzepatide supports sustained weight loss over a long duration (112 weeks). When compared to the placebo group, both tirzepatide arms showed statistically significant improvements. Specifically, the MTD arm demonstrated an estimated treatment difference (ETD) of -12.0% versus placebo, and the 5 mg arm showed an ETD of -6.6% versus placebo.

Methodological limitations include the lack of reported data regarding serious adverse events or specific discontinuation rates. Additionally, the study did not report any other specific limitations in the provided documentation. However, the high certainty of the primary outcome is supported by the Phase 3b randomized controlled trial design.

Clinically, these results suggest that continuing tirzepatide at the maximum tolerated dose is an effective strategy for maintaining weight reduction over a period exceeding one year. For patients who may not tolerate the MTD, reducing the dose to 5 mg provides a documented alternative to treatment discontinuation, as it still yields a -16.6% weight reduction. Clinicians should note that individual responses vary when transitioning to lower doses.

Questions remain regarding the long-term impact on other metabolic markers beyond weight and the specific characteristics of patients who may experience more severe gastrointestinal events during dose escalation.

How this fits prior evidence

How this fits prior evidence: This study confirms previous findings that tirzepatide at maximum tolerated dose leads to significant weight reduction in obesity. It extends the clinical utility of the medication by providing data on a 112-week follow-up period, showing that MTD maintains a -21.9% bodyweight reduction. The results also provide an alternative for patients who cannot tolerate high doses, as the 5 mg dose still achieved a -16.6% reduction compared to the -9.9% seen in placebo.

Managing weight is a lifelong journey for many people living with obesity. For those who have struggled to keep weight off after initial efforts, finding a sustainable way to maintain progress is a major concern. This study looked specifically at how the medication tirzepatide performs over a long period—nearly two years—to see if it could help patients maintain their results rather than regaining weight.

Researchers conducted a large-scale trial involving 378 adults who were living with obesity. The participants were divided into groups to receive different amounts of tirzepatide or a placebo (a substance with no medicinal effect). One group received the maximum tolerated dose, another received a lower dose of 5 mg, and the third group received the placebo. The study was designed to track weight changes over 112 weeks, which is about two years, providing a much longer window than many typical clinical trials.

The results showed that those taking tirzepatide experienced significant weight loss compared to those taking the placebo. Specifically, patients on the maximum dose lost about 21.9% of their body weight by the end of the study. Those on the lower 5 mg dose also saw substantial progress, losing about 16.6% of their body weight. In contrast, the group taking the placebo saw much less change. Importantly, the study found that even when the dosage was adjusted or maintained over time, the medication continued to help patients keep the weight off compared to those not taking it.

Regarding safety, most people who took the medication experienced gastrointestinal issues, such as nausea or upset stomach. However, these side effects were generally mild to moderate and mostly happened while the dose was being increased at the start of treatment. No serious safety concerns were reported in the data provided.

It is important to remember that while these results are very encouraging, every person's body reacts differently to medication. This study shows a clear trend for the group as a whole, but individual results can vary. Because this was one specific trial, it does not mean everyone will see the exact same percentage of weight loss.

For patients today, this means that tirzepatide is showing strong potential as a long-term tool for weight management. It suggests that the medication can be effective not just for initial weight loss, but for maintaining those results over many months. Patients should speak with their doctors to see if this treatment fits their specific health goals and history.

What this means for you:
Tirzepatide showed significant and sustained weight loss over two years compared to a placebo in an adult study.

Study Details

Study typeRct
Sample sizen = 441
EvidenceLevel 2
Follow-up25.9 mo
PublishedJun 2026
View Original Abstract ↓
BACKGROUND: Obesity treatment improves long-term health and quality of life outcomes. Weight reduction and its maintenance play an important role in achieving these goals. We evaluated the efficacy and safety of continuing tirzepatide at the maximum tolerated dose (MTD) or lowering the dose to 5 mg compared with switching to placebo on the maintenance of bodyweight reduction obtained with tirzepatide MTD in adults with obesity. METHODS: This phase 3b, placebo-controlled, 112-week trial, including a 60-week open-label weight-loss period and a 52-week, double-blind weight maintenance period, was conducted across 20 sites in the USA. After completing the initial weight-loss period with once weekly subcutaneous tirzepatide at the MTD (10 mg or 15 mg), adults (aged ≥18 years) with a BMI of 30 kg/m and above or 27 kg/m and above with one or more weight-related comorbidity, and a history of at least one self-reported unsuccessful dietary effort to lose bodyweight were randomly assigned in a 3:3:2 ratio to continue tirzepatide MTD, reduce to tirzepatide 5 mg, or switch to placebo for an additional 52 weeks. Starting at week 84 (24 weeks after random allocation), participants could receive rescue tirzepatide if their weight regain exceeded 50%. The primary endpoint was the percentage change in bodyweight from baseline to week 112. The primary estimand was the modified treatment-regimen estimand, which assumed that participants who initiated rescue tirzepatide would not have gained further benefit from their assigned study treatment and included all randomly allocated participants, regardless of treatment discontinuation or initiation of prohibited medications. The efficacy estimand was supportive. Safety was assessed in all participants who received at least one dose of study drug. This completed trial was registered at ClinicalTrials.gov (NCT06047548). FINDINGS: From Sept 20, 2023, to Jan 20, 2026, 441 patients were enrolled in and took at least one dose of study treatment during the weight-loss period, with 378 participants randomly allocated at week 60 (140 to tirzepatide MTD; 144 to dose-reduction to 5 mg tirzepatide; and 94 to placebo). 372 received at least one dose of study drug during the weight maintenance period (139 for tirzepatide MTD; 142 for 5 mg tirzepatide; and 91 for placebo). 345 (91%) of 378 participants completed the study. The majority of participants were White (67%); 288 (65%) participants were female and 153 (35%) were male; and the mean age was 46·6 years (SD 13·0). At baseline, participants had a mean bodyweight of 113·8 kg (SD 27·0), a BMI of 40·1 kg/m (SD 8·1), and HbA 5·64% (SD 0·4; 38·2 mmol/mol [SD 4·0]). The model-based estimate percent change in bodyweight from baseline to week 112 was -21·9% (95% CI -23·5 to -20·3) with MTD (estimated treatment difference [ETD] -12·0% [95% CI -13s·8 to -10·1]), -16·6% (95% CI -18·0 to -15·1) with 5 mg tirzepatide (ETD -6·6 [95% CI -8·3 to -5·0]), versus -9·9% (95% CI -11·1 to -8·8) with placebo (p<0·0001 for all comparisons). Among participants who regained at least 50% of lost bodyweight, observed means were 11 (8%) of 138, 35 (25%) of 142, and 60 (67%) of 90 participants received rescue therapy in the tirzepatide MTD, 5 mg tirzepatide, and placebo, respectively. The most common adverse events with tirzepatide were gastrointestinal events, which were mostly mild to moderate in severity and mostly occurred during dose escalation. INTERPRETATION: In adults with obesity, long-term treatment is often necessary to maintain bodyweight reduction and its associated cardiometabolic benefits. In the SURMOUNT-MAINTAIN trial, continuing tirzepatide at MTD maintained bodyweight reduction and health-related benefits. Reducing to 5 mg tirzepatide might provide a valuable alternative to discontinuation, although individuals' treatment response might vary. Together, these findings support the importance of ongoing therapy for long-term obesity management and provide evidence to inform individualised, patient-centred obesity care. FUNDING: Eli Lilly.
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