In direct head-to-head trial data, Mounjaro (tirzepatide) produces greater average weight loss and a larger reduction in waist circumference than Wegovy (semaglutide). Wegovy has a specific advantage of its own, however: it's the only one of the two with a UK licence for reducing cardiovascular risk, based on a major trial in which almost three-quarters of participants were men. Neither is simply "better" — the right choice depends on whether maximum weight loss or a proven cardiovascular indication matters more for your situation, which is exactly what your consultation is for.
A 2025 randomised trial compared tirzepatide and semaglutide directly in adults with obesity but without diabetes, using the maximum tolerated dose of each. Tirzepatide (Mounjaro) was superior to semaglutide (Wegovy) for both body weight reduction and waist circumference reduction at 72 weeks — the waist circumference finding is particularly relevant for men, given how closely abdominal fat tracks cardiometabolic risk in male patients specifically.
| Mounjaro | Wegovy Injection | |
|---|---|---|
| Active ingredient | Tirzepatide | Semaglutide |
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
| Average weight loss (highest dose)* | ~22.5% | ~14.9% (2.4mg) / ~17.4–20.7% (7.2mg) |
| Head-to-head result | Superior weight and waist circumference reduction vs semaglutide | — |
Wegovy holds a UK licence that Mounjaro does not: a specific indication for reducing cardiovascular risk in adults with overweight or obesity and existing cardiovascular disease. This is based on the SELECT trial, one of the largest cardiovascular outcomes studies conducted in this field, which enrolled over 17,000 participants — 72% of them men — with a prior heart attack, stroke or peripheral artery disease. Semaglutide reduced major adverse cardiovascular events by 20% compared with placebo, and follow-up analysis found this benefit occurred independently of how much weight participants actually lost, suggesting a cardioprotective effect beyond weight loss alone.
Why this matters for men specifically
Cardiovascular disease risk factors, including central obesity, are more common in men, and the SELECT trial population reflects that reality — nearly three in four participants were men. If you have an existing heart condition or a strong family history of cardiovascular disease, this licensed indication is a genuine point of difference, not just a footnote.
Real-world studies covered in our main men's guide show that GLP-1 treatments as a class — including both tirzepatide and semaglutide — are associated with rising testosterone levels in men who lose significant weight, most likely because the weight loss itself reverses the specific, obesity-driven pattern of low testosterone described in that guide. The evidence to date doesn't point to one drug having a specific testosterone advantage over the other — the effect appears tied to the amount of weight lost rather than the particular medicine used to lose it.
Mounjaro may suit you if…
- Maximum average weight loss is your priority, based on head-to-head trial data
- Waist circumference reduction is a specific goal alongside overall weight loss
- You have no contraindications to dual GIP/GLP-1 receptor agonists
Wegovy may suit you if…
- You have existing cardiovascular disease, or a strong family history of it
- You want the GLP-1 medicine with the longest UK real-world safety track record
- Your prescriber identifies a specific reason to prefer a GLP-1-only mechanism over a dual agonist
Both medicines share a broadly similar side-effect profile, since they act on overlapping appetite-regulating pathways. The most commonly reported effects for both are nausea, constipation, diarrhoea and reduced appetite, particularly during the first few weeks after a dose increase. Mounjaro's dual mechanism may produce slightly more pronounced early gastrointestinal effects for some men, though this varies considerably by individual.
Important
This is a general comparison, not medical advice. Suitability for either treatment depends on your full medical history, including any history of pancreatitis, gallbladder disease, thyroid cancer or diabetic retinopathy. Always disclose your full history during your consultation.
Not Sure Which Is Right For You?
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- Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. N Engl J Med. 2025;393(1):26–36.
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022.
- Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). N Engl J Med. 2023;389:2221–2232.
- Semaglutide for cardiovascular event reduction in people with overweight or obesity: SELECT study baseline characteristics. 2022.
- Semaglutide and cardiovascular outcomes by baseline and changes in adiposity measurements: prespecified SELECT analysis. Lancet. 2025.
- Endocrine Society. Anti-obesity medications can normalize testosterone levels in men. ENDO 2025 press release.
- MHRA. Wegovy Summary of Product Characteristics — cardiovascular risk reduction indication.