# Tirzepatide Weight Loss: The Trial Evidence — Tirzepatide Chemical > Tirzepatide weight loss results from SURMOUNT-1, SURMOUNT-5, and the full programme: up to -20.9% body weight at 72 weeks. The randomised trial data, cited and explained. ## The short version Tirzepatide weight loss results are the largest produced by any approved medication in phase 3 randomised trials. In the biggest trial of its kind — 2,539 adults with obesity and no diabetes — people on the highest dose lost about 21% of their starting body weight over 72 weeks, compared with about 3% for placebo. A head-to-head trial against a selective GLP-1 receptor agonist found tirzepatide produced 47% more weight loss over the same period. The weight loss is not just about a number on a scale: blood pressure, LDL-cholesterol, triglycerides, and sleep apnea markers all improved in the same trials. This page summarises the weight and cardiometabolic evidence from the published randomised trials, with every number traced to a specific study. ## Tirzepatide weight loss: SURMOUNT-1 results SURMOUNT-1 is the registrational phase 3 trial establishing tirzepatide weight loss efficacy in adults without diabetes. The trial enrolled 2,539 adults with obesity (BMI ≥30) or overweight (BMI ≥27) with a weight-related complication, randomised to once-weekly tirzepatide 5, 10, or 15 mg or placebo, with a 20-week dose-escalation period followed by maintenance through 72 weeks. Mean percentage weight change at week 72 [4]: - **5 mg**: -15.0% versus -3.1% with placebo - **10 mg**: -19.5% versus -3.1% - **15 mg**: -20.9% versus -3.1% The most common adverse events were gastrointestinal (nausea, vomiting, diarrhoea, constipation) and were mostly mild to moderate, occurring primarily during dose escalation [4]. These are the tirzepatide results that drove the November 2023 FDA approval for chronic weight management. ## Tirzepatide results head-to-head: SURMOUNT-5 SURMOUNT-5 was the first phase 3 head-to-head trial of tirzepatide directly against a selective GLP-1 receptor agonist in adults with obesity but without diabetes. The trial randomised 751 adults to the maximum tolerated dose of tirzepatide (10 or 15 mg) or the maximum tolerated dose of the comparator (1.7 or 2.4 mg) once weekly for 72 weeks. Least-squares mean weight change at week 72 [5]: - **Tirzepatide**: -20.2% - **Selective GLP-1 comparator**: -13.7% - **Difference**: -6.5 percentage points (P<0.001) Tirzepatide also produced a greater reduction in waist circumference and higher proportions of participants reaching ≥10%, ≥15%, ≥20%, and ≥25% weight loss thresholds [5]. These tirzepatide results confirm the head-to-head superiority seen in type 2 diabetes (SURPASS-2) extends to the obesity-without-diabetes population. ## Tirzepatide vs semaglutide: what the trials measured Three trials now compare tirzepatide directly against semaglutide (a selective GLP-1 receptor agonist) as an active comparator. Results are consistent across populations: **In type 2 diabetes (SURPASS-2, 40 weeks)**: - HbA1c: tirzepatide superior at all three doses (2.01/2.24/2.30 vs 1.86 percentage-point reduction) [3] - Body weight: tirzepatide produced 1.9, 3.6, and 5.5 kg more reduction than the comparator [3] **In obesity without diabetes (SURMOUNT-5, 72 weeks)**: - Body weight: tirzepatide -20.2% versus comparator -13.7% [5] **In clinical practice (Nat Med 2026, five US cohort studies with propensity-score matching)**: - For MI/stroke/all-cause mortality, tirzepatide versus a GLP-1 comparator: HR 1.06 (95% CI 0.95-1.18) — no statistically significant cardiovascular advantage in this observational analysis [14] The mechanistic advantage of the dual-receptor target is well-established in the trial programme; the cardiovascular outcomes advantage in head-to-head comparison requires the ongoing SURPASS-CVOT data for definitive characterisation. ## Cardiometabolic effects beyond weight: blood pressure, lipids, and cardiorenal outcomes The weight reduction is the most visible tirzepatide result, but cardiometabolic markers improve across the board in the trial record. **Blood pressure** — A pooled SURPASS-programme analysis reported clinically meaningful systolic blood-pressure reductions across the programme [8]. A meta-analysis of seven randomised controlled trials quantified the dose-response: systolic blood pressure fell -4.20 mmHg (5 mg), -5.34 mmHg (10 mg), and -5.77 mmHg (15 mg); diastolic blood pressure, LDL-cholesterol, and triglycerides also fell, while HDL-cholesterol rose across doses [10]. **Cardiorenal outcomes** — The SURPASS-CVOT post-hoc analysis found tirzepatide was associated with a 16% lower incidence of a broad six-component cardiovascular-and-kidney composite endpoint versus a GLP-1 receptor agonist comparator in type 2 diabetes patients with established cardiovascular disease (HR 0.84) [13]. **Obstructive sleep apnea** — The SURMOUNT-OSA trial (Malhotra et al., 2024) reported that tirzepatide produced significant reductions in the apnea-hypopnea index (the number of apnea events per hour), earning an FDA approval specifically for moderate-to-severe obstructive sleep apnea in adults with obesity [15]. **MASH/heart failure** — Loomba et al. (2024) reported that tirzepatide improved histological endpoints in metabolic dysfunction-associated steatohepatitis (MASH, a progressive fatty-liver disease) with liver fibrosis [12]. Packer et al. (2025) reported significant reductions in heart failure symptoms and physical limitations in the SUMMIT trial of heart failure with preserved ejection fraction and obesity [16]. For details on what people report — including adverse effects — see [Tirzepatide effects](/effects). ## Why am I not losing weight on tirzepatide? Weight loss plateaus are a documented pattern in the trial data and in clinical practice. SURMOUNT-1 showed that weight loss occurs in a non-linear arc: most weight reduction happens in the first 36-52 weeks and then slows. Contributing factors documented in the trial literature include: metabolic adaptation (the body reduces energy expenditure as weight falls), dietary drift (appetite-suppression often attenuates after the initial months), and the dose being below the participant's effective maintenance dose. SURMOUNT-4 (Aronne et al., 2024) specifically demonstrated that participants switched to placebo after 36 weeks of tirzepatide regained weight — on average about 11.8% of starting body weight returned — while those continuing on the active arm continued losing [18]. --- The chemistry and trial record of a dual-receptor agonist, read independently — no clinic, no product, no prescription.