One published case did, and that is the whole of the direct evidence. A man of 40 with class 2 obesity lost under 5% over six months on tirzepatide 15 mg. He then lost 20% over the next six months on semaglutide 2.4 mg [1]. Every comparison of the two molecules runs the other way on average, which is what the tirzepatide premium on almost every seller here is priced against. An average is not a promise to any individual.
What happened to the one patient
He started at a body mass index of 39.8 with a HOMA-IR of 5.0, against a reference under 2.0. Tirzepatide was escalated to the top dose of 15 mg weekly and held there. Six months later he had lost under 5%.
Switched to semaglutide 2.4 mg weekly, he lost 20% over the following six months. Fasting glucose normalized, insulin resistance resolved, and he reported appetite control he had not had on the other drug.
What the comparisons say on average
A retrospective study of 183 Chinese adults with obesity and no diabetes ran three months at one hospital clinic [2]. Tirzepatide came out 2.87 kg ahead, 95% CI 1.32 to 4.41, p < 0.001. The share passing 10% weight loss was 21.50 percentage points higher, 95% CI 7.45 to 35.55.
The doses are the thing to notice. Semaglutide was given at 1.7 mg, one rung below the 2.4 mg licensed for weight. Tirzepatide was given at 5 mg, the lowest of its three maintenance doses. So the comparison chose a near-top dose of the drug that lost and the entry dose of the drug that won. Food cravings and appetite regulation were comparable between them, on two validated questionnaires, which is the interesting null.
A larger new-user cohort followed 14,046 American adults with a BMI of 30 or more [3]. At twelve months, mean weight change was −13.0% on tirzepatide against −5.9% on semaglutide, with three older drugs clustered near −4.0%. The ordering matched the randomized trials. The magnitudes did not, which is the gap described in how long a GLP-1 takes to work.
What the case is good for
Not choosing a molecule. One patient cannot do that, and the averages still run the other way. What it is good for is pricing a certainty that does not exist.
Paying a premium for tirzepatide buys a higher expected result. An expectation is not a guarantee that the dearer drug will do anything for a particular person. Sellers do not price that risk, because they cannot. The spread between the two molecules is in the switch in the other direction.
What not to do with it
Do not read this as a reason to switch, or as a reason to start on the cheaper molecule to see what happens. Neither follows from one patient, and neither is a decision a price list should make.
What does follow is narrower. An expensive drug at a top dose doing nothing after six months is information. It belongs with whoever is prescribing, rather than with an escalating bill. What the market charges for each molecule is counted in what a GLP-1 costs per month.