Accepted answer
The short version: the effect is real, the magnitude depends on the population, and the population is usually the part that gets dropped when a result is quoted second-hand.
Placebo arms in this class are not nothing. Lifestyle-intervention placebo arms in the major obesity trials commonly lose two to three per cent of body weight, so an active-arm figure quoted without its comparator overstates the drug effect by roughly that much.
Headline results, principal programmes
| Trial | Agent | n | Duration | Primary result |
|---|
| STEP 1 | Semaglutide 2.4 mg | 1,961 | 68 wk | −14.9 % vs −2.4 % weight |
| STEP 2 | Semaglutide 2.4 mg, T2DM | 1,210 | 68 wk | −9.6 % vs −3.4 % weight |
| SURMOUNT-1 | Tirzepatide 5/10/15 mg | 2,539 | 72 wk | −15 / −19 / −21 % weight |
| SURMOUNT-4 | Tirzepatide, withdrawal | 670 | 88 wk | Continued loss vs substantial regain |
| SELECT | Semaglutide 2.4 mg | 17,604 | ~40 mo | MACE HR 0.80 (0.72–0.90) |
| FLOW | Semaglutide 1.0 mg, CKD | 3,533 | ~3.4 yr | Renal composite reduced; stopped early |
| SURMOUNT-OSA | Tirzepatide, OSA | 469 | 52 wk | AHI reduced with and without PAP |
Worth being precise here: a composite endpoint is only as informative as its least serious component. Where a cardiovascular composite combines death, infarction and stroke, ask which component moved, because they are not interchangeable outcomes.
Registry entries at ClinicalTrials.gov carry the pre-specified primary endpoint with a timestamp, which is the cheapest available check on whether an endpoint was changed after the data were seen.
I am not a clinician and this is not medical advice; it is a reading of a published protocol.
The short version: check the endpoint, check the comparator, check who was excluded, then look at the number.