Short answer: Semaglutide primarily activates the GLP-1 receptor. Tirzepatide activates GIP and GLP-1 receptors. Both have been studied clinically, but results and approved uses belong to specific medicines, formulations and populations.

Start with the research question

A comparison is incomplete unless it states what is being compared. Weight change, glucose control, cardiovascular outcomes, tolerability and treatment persistence are different endpoints. A medicine can perform differently across those outcomes. A trial in adults without diabetes should not be treated as a complete answer for people with diabetes, adolescents or another clinical population.

The 2025 SURMOUNT-5 study directly compared tirzepatide and semaglutide in adults with obesity without type 2 diabetes. It was randomized and open-label, meaning participants and investigators knew the assigned treatment. Tirzepatide produced greater average reductions in body weight and waist circumference at 72 weeks in that study. Gastrointestinal adverse events were the most common harms in both groups; most were mild or moderate and occurred during dose escalation. The trial was funded by Eli Lilly. These details matter when interpreting the result. SURMOUNT-5 original trial

Averages are not individual forecasts

A group average summarizes a distribution. Some participants respond more, some less, and some stop treatment. A useful article should report who was studied, what happened to participants who discontinued, and the harms observed, rather than presenting a headline as a personal forecast.

The receptor difference helps explain why the compounds are scientifically distinct. Structural studies show that tirzepatide interacts with both incretin receptors and that its signaling is not simply equivalent to placing the two natural hormones together. Those experiments inform mechanism; they do not replace clinical comparison. Tirzepatide receptor study

Product identity still matters

An approved medicine and an unapproved preparation with a similar label are not the same evidentiary object. FDA warns that unapproved versions of GLP-1 drugs do not undergo its premarket review for safety, effectiveness and quality. FDA safety information

For a reader, the practical research skill is to separate four questions: What molecule is this? What exact product was tested? In whom? For which outcome? Choosing a prescription treatment is a clinical decision, not something a comparison article can make from a reader's search query.