Adding the clinical framing, because it changes how the question reads. If two explanations both fit, the useful question is which one predicts something the other does not. That is answerable; arguing about which sounds more plausible is not.

dave_SLC said:

Say what you would expect to see if you were wrong, before you look.

There is a second half to this that has not been said yet. SURMOUNT-1 landed around 20.9% mean weight loss at 15mg over 72 weeks, against roughly 15% for semaglutide 2.4mg in STEP 1. Different trials, different populations, so the comparison is indicative rather than decisive — but SURPASS-2 was a genuine head-to-head and it pointed the same way.

The figures, for anyone assembling their own picture. Worth stating the units and the reference range whenever you post a number here. A large fraction of the apparent disagreement in these threads is two people using different units and both being right.

One thing that is still open after dave_SLC’s answer:

How much of the tirzepatide advantage is the GIP component and how much is simply that the dose ladder goes higher in receptor-occupancy terms?

Moderator note: a couple of off-topic posts removed. Tagging this one for the weekly digest.