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Randomized controlled trial

SURMOUNT-MAINTAIN: keeping weight off on tirzepatide

At week 112, weight had changed by −21.9% on the maximum tolerated dose of tirzepatide, −16.6% on 5 mg and −9.9% on placebo; the differences versus placebo were −12.0 percentage points (95% CI, −13.8 to −10.1) and −6.6 points (95% CI, −8.3 to −5.0), both p < 0.0001.

Horn DB et al. Tirzepatide for maintenance of bodyweight reduction in people with obesity in the USA (SURMOUNT-MAINTAIN): a multicentre, double-blind, randomised, placebo-controlled trial. The Lancet, 2026. DOI: 10.1016/S0140-6736(26)00656-2

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Key facts

Drug
tirzepatide
Design
Randomized controlled trial
Participants
378
Duration
112 weeks
Funding
Eli Lilly
Registry
NCT06047548
Population
441 adults with obesity (BMI of 30 or more, or 27 or more with at least one weight-related complication) and without diabetes (per the registry) started 60 weeks of open-label tirzepatide at the maximum tolerated dose (10 or 15 mg) at 20 sites in the United States; 378 were then randomized to stay on that dose (140), step down to 5 mg (144) or switch to placebo (94). At baseline, 65% were women, mean age was 46.6 years, mean weight 113.8 kg and mean BMI 40.1.
Primary outcome
Percentage change in weight from the start of the study to week 112 (52 weeks after randomization) when staying on the maximum tolerated dose of tirzepatide or stepping down to 5 mg once weekly, versus switching to placebo. From week 84, participants who regained more than 50% of the weight they had lost could receive rescue tirzepatide.

What it found

At week 112, weight had changed by −21.9% on the maximum tolerated dose of tirzepatide, −16.6% on 5 mg and −9.9% on placebo; the differences versus placebo were −12.0 percentage points (95% CI, −13.8 to −10.1) and −6.6 points (95% CI, −8.3 to −5.0), both p < 0.0001. The figures are measured from the weight before tirzepatide, so they include what was lost in the 60 weeks before randomization. Of the randomized participants, 91% completed the study. The most common adverse effects on tirzepatide were digestive, mostly mild or moderate and concentrated in the dose-escalation phase.

Limitations

Funded by Eli Lilly, which makes tirzepatide. Only people who completed and tolerated 60 weeks at the maximum dose were randomized, all in the United States, which may overstate maintenance in practice. The randomized phase lasted 52 weeks, and the rescue tirzepatide allowed from week 84 complicates the comparison between groups. The Lancet published a correction (the placebo denominator for rescue use and one figure) that does not change the figures cited here.

What it means for you

SURMOUNT-MAINTAIN looked at what happens after weight loss on tirzepatide: counting from before treatment began, weight had changed by −21.9% in those who stayed on the maximum tolerated dose, −16.6% in those who stepped down to 5 mg and −9.9% in those switched to placebo. Only people who had tolerated 60 weeks at the maximum dose took part, so it may overstate what happens in practice. Whether staying on a dose or lowering it makes sense for you is a decision for your doctor.

Further reading

Related trials

  • tirzepatide72 weeks

    SURMOUNT-1 (body composition)

    At 72 weeks, weight changed by −21.3%, fat mass by −33.9% and lean mass by −10.9% with tirzepatide, compared with −5.3%, −8.2% and −2.6% on placebo.

  • tirzepatide and semaglutide72 weeks

    SURMOUNT-5

    At 72 weeks, weight fell by 20.2% with tirzepatide and 13.7% with semaglutide.

  • tirzepatide88 weeks

    SURMOUNT-4

    From week 36 to week 88, weight changed by −5.5% in those who stayed on tirzepatide and by +14.0% in those switched to placebo.

  • tirzepatide52 weeks

    SURMOUNT-OSA

    At 52 weeks, the AHI fell by 25.3 events per hour with tirzepatide and 5.3 with placebo in trial 1, and by 29.3 versus 5.5 in trial 2.

Sources

The original paper and the records consulted for this summary, with the date they were accessed.

  1. The Lancet.Horn DB, et al. Tirzepatide for maintenance of bodyweight reduction in people with obesity in the USA (SURMOUNT-MAINTAIN). Lancet. 2026;407(10545):2305-2318.accessed .
  2. National Library of Medicine (PubMed).PubMed record PMID 42119587 (abstract).accessed .
  3. The Lancet.Department of Error. Lancet. 2026;407(10545):2290 (correction to SURMOUNT-MAINTAIN).accessed .
  4. ClinicalTrials.gov (National Library of Medicine).ClinicalTrials.gov record NCT06047548 (registration, eligibility and sites).accessed .