Tirzepatide after intensive lifestyle intervention in adults with overweight or obesity: the SURMOUNT-3 phase 3 trial
Wadden TA, Chao AM, Machineni S, Kushner R, Ard J, Srivastava G
Nature Medicine (2023) · n=579
After a 12-week intensive lifestyle lead-in produced ≥5% weight loss, tirzepatide produced an additional 18.4% weight reduction over 72 weeks versus 2.5% on placebo — a total program effect of 24.3% from study start, the largest published response to a lifestyle-plus-pharmacotherapy obesity protocol.
SURMOUNT-3 is the third pivotal Phase 3 trial in the SURMOUNT program, designed to answer a clinically relevant question that SURMOUNT-1 and SURMOUNT-2 did not address: how much additional weight loss does tirzepatide produce on top of a structured lifestyle intervention? Investigators enrolled 806 adults with BMI ≥30 kg/m² (or ≥27 with at least one weight-related complication, excluding diabetes) into a 12-week intensive lifestyle intervention featuring a 1,200-1,500 kcal/day diet, ≥150 minutes/week of physical activity, and behavioral counseling. The 579 participants (287 tirzepatide, 292 placebo) who achieved ≥5% weight loss during the lead-in were then randomized to maximum-tolerated-dose tirzepatide (10 or 15 mg) or placebo for 72 weeks of double-blind treatment. The coprimary endpoint was mean percent body-weight change from randomization to week 72. Mean additional weight change was -18.4% on tirzepatide versus +2.5% on placebo (treatment difference -20.8 percentage points, p < 0.001) — meaning that placebo participants regained weight on average, while tirzepatide participants nearly doubled their lifestyle-induced loss. Cumulative weight loss from the start of the lifestyle lead-in through week 72 was 24.3% on tirzepatide versus 4.5% on placebo. The categorical coprimary endpoint (≥5% additional reduction) was met by 87.5% of tirzepatide participants versus 16.5% of placebo. Adverse events occurred in 87.1% of tirzepatide-treated participants versus 76.7% of placebo, dominated by mild-to-moderate gastrointestinal events.
The "intensive lifestyle intervention" lead-in is more structured than what most patients receive in real-world clinical care — 12 weeks of trial-grade dietary and behavioral support is uncommon outside academic obesity clinics, and the 5% weight-loss responder population that proceeded to randomization is a positively selected subset (only 71% of lead-in enrollees met the threshold and entered the randomized phase). Both factors mean the 24.3% total program weight loss represents an upper bound for a highly motivated, lifestyle-responsive cohort rather than a typical clinical-practice expectation. Placebo recipients regaining weight on average despite continued counseling is itself notable — it reinforces the documented difficulty of maintaining lifestyle-only weight loss past the initial responder phase. As with SURMOUNT-1 and -2, the demographics skew predominantly White. Industry sponsorship by Eli Lilly is disclosed, and an author correction was issued in 2024 (Nature Med 30:1190).
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