As the headline weight-loss numbers in the obesity-drug race keep climbing, a quieter result points at the question those numbers obscure: which drug prevents more heart attacks and strokes? A large real-world study called STEER, published in *Diabetes, Obesity and Metabolism* in 2026, found that semaglutide was associated with a 29% lower risk of major adverse cardiovascular events than tirzepatide in patients with established cardiovascular disease—a result that runs in the opposite direction from the weight-loss data, and one worth reading carefully in both respects.
What STEER Found
STEER was a retrospective, observational cohort study using Komodo Research claims data. It included patients 45 and older with overweight or obesity and established atherosclerotic cardiovascular disease—a prior heart attack, ischemic stroke, or peripheral artery disease—and without diabetes, who started either semaglutide or tirzepatide between May 2022 and January 2025. After propensity-score matching to balance baseline characteristics, each arm held 10,625 patients.
On the three-point composite of heart attack, stroke, and all-cause death, semaglutide was associated with a 29% lower risk than tirzepatide (hazard ratio 0.71; p = 0.046). On a broader five-point composite that added coronary revascularization and heart-failure hospitalization, semaglutide showed a 22% lower risk (hazard ratio 0.78; p = 0.040). Both results cleared statistical significance, though both p-values sit just under the 0.05 threshold.
Why This Is Interesting—and Why It Is Not Settled
Here is the tension worth sitting with. On weight loss, the head-to-head SURMOUNT-5 trial put tirzepatide clearly ahead—20.2% versus 13.7% over 72 weeks. STEER suggests that on cardiovascular events, the ranking may flip. If both hold, it would mean the drug that takes off more weight is not automatically the drug that prevents more cardiovascular events, and that molecule-specific effects beyond weight loss are doing real work. That is a genuinely important possibility for anyone treating cardiometabolic disease.
But STEER cannot establish it, and the study’s own design is the reason. This is observational claims data, not a randomized trial. Propensity matching balances the characteristics you can measure; it does nothing for the ones you cannot, and residual confounding is the standing hazard of every study of this kind. The outcomes are derived from insurance claims rather than adjudicated clinical events. And both p-values land just beneath significance, which is not a reason to dismiss the finding but is a reason not to over-read it. STEER generates a serious hypothesis. It does not close the question.
The only thing that closes it is a head-to-head randomized cardiovascular-outcomes trial, and that trial has not been run. Until it is, the honest statement is that semaglutide has the longer and stronger dedicated cardiovascular-outcomes record—anchored by SELECT—while tirzepatide’s cardiovascular-outcomes evidence is still maturing, and a direct randomized comparison on hard outcomes does not yet exist.
What This Means for You
If you or someone you advise has established heart disease: this is the population STEER actually studied, and it is the population where the choice between these drugs may matter most. The finding is a reason to make cardiovascular risk—not just the weight-loss percentage—part of the conversation with a prescriber. It is not a reason to switch drugs on the strength of one observational study.
If you are comparing these drugs for weight loss alone: STEER does not change the weight-loss picture. Tirzepatide’s superiority on that endpoint comes from a randomized head-to-head trial, which is stronger evidence than STEER’s observational design.
The broader point: as efficacy converges at the top of this market, the differentiation that will matter is outcomes data—events prevented, not pounds lost. STEER is an early, imperfect look at that future. Expect a great deal more of this kind of comparison, and read each one for its design before its headline.
References
- Wilson, et al. “Semaglutide and tirzepatide effects on cardiovascular outcomes in people with overweight or obesity in the real world (STEER).” *Diabetes, Obesity and Metabolism*, 2026. https://doi.org/10.1111/dom.70436
- “Semaglutide Superior to Tirzepatide in Reducing Cardiovascular Event Risk.” The Cardiology Advisor, 2026. https://www.thecardiologyadvisor.com/news/semaglutide-superior-to-tirzepatide-in-reducing-cardiovascular-event-risk/
- “Real-World Data Point to Greater Impact of Semaglutide Over Tirzepatide in Reducing Heart Attack, Stroke Risk.” NeurologyLive, 2026. https://www.neurologylive.com/view/real-world-data-points-greater-impact-semaglutide-over-tirzepatide-reducing-heart-attack-stroke-risk
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