Evidence review · from the 250-topic plan
STEP 1, reread: the trial that started the era — and still prices the value pick
STEP 1 randomized about 1,960 adults with obesity — no diabetes — to weekly semaglutide 2.4 mg or placebo for 68 weeks: roughly 14.9% average weight loss versus 2.4%, with about a third of treated participants clearing 20%. Blood pressure, lipids and glycemia improved alongside; GI side effects were escalation-clustered and mostly mild-to-moderate. Two later chapters complete the file: the extension's regain (~two-thirds of lost weight back within a year off) and SELECT's cardiovascular-outcomes result for the molecule. In the tirzepatide era, 14.9% is no longer the ceiling — but at an audited $1,428/year, it remains the field's most defensible dollars-per-percent.
The design that set the template
Published in NEJM in 2021, STEP 1 enrolled adults with BMI 30+ (or 27+ with a weight-related condition), excluding diabetes, and randomized two-to-one to semaglutide 2.4 mg weekly or placebo — both with lifestyle counseling — for 68 weeks, titrating up the 0.25→2.4 ladder over sixteen weeks. Its structure became the genre's grammar; every SURMOUNT you've read on this site is written in it.
The results, with their texture
Average loss ~14.9% versus ~2.4% — at publication, the largest pharmacotherapy result obesity medicine had produced. Distribution: about 86% of treated participants cleared 5%, ~69% cleared 10%, and roughly a third cleared 20% — against ~2% of placebo. Discontinuation for GI events sat in the low-to-mid single digits, with nausea's usual escalation clustering. The plateau's shape — steep through month eight, bending after — is the curve every "why did I stall?" question should be graded against.
Beyond the scale
Systolic blood pressure fell on the order of six points versus placebo; triglycerides, waist circumference, HbA1c and inflammatory markers moved with it; physical-function scores improved. The trial's quiet thesis — that treating weight treats the metabolic cluster around it — was later promoted to proof by the outcomes era: SELECT's ~20% cut in major cardiovascular events belongs to this molecule, and no competitor's file yet holds its equal.
The after-chapters that complete the file
The extension answered "what if I stop": about two-thirds of lost weight regained within a year off therapy, cardiometabolic gains reverting alongside — chronic-condition biology, covered in full in the stopping piece. Read together, STEP 1 and its extension say the same thing SURMOUNT-1 and SURMOUNT-4 say about tirzepatide: the results are real, and they are rented for as long as treatment lasts.
Reading 14.9% in the tirzepatide era
The head-to-head (SURMOUNT-5) puts tirzepatide's average about 6.5 points higher at maximum tolerated doses. What that does not do is retire this trial. Semaglutide keeps three live claims: the cardiovascular-outcomes certificate, the longer prescribing history — and the price. Audited field floor: $119/month, $1,428/year all-in, dose-proof; the tirzepatide flat runs $240/year more. Per percentage point of trial-average loss, the value molecule still wins the arithmetic — which is exactly the kind of sentence a shopper needs and a marketer omits. The audited semaglutide floor ↗
FAQ
What did STEP 1 show?
~14.9% average weight loss with weekly semaglutide 2.4 mg over 68 weeks versus ~2.4% on placebo, with about a third of treated participants losing 20%+ and cardiometabolic markers improving alongside.
How does STEP 1 compare to SURMOUNT-1?
Different trials, same grammar: semaglutide's 14.9% versus tirzepatide's 15–20.9% dose-response — with the direct comparison later run in SURMOUNT-5 (~13.7% vs ~20.2%).
Is semaglutide still worth choosing?
For many shoppers, yes: the cardiovascular-outcomes evidence, the longest weight-management track record, and the field's lowest audited all-in price at $119/month.
Does compounded semaglutide carry STEP 1's certificate?
No — it shares the intended active ingredient; the trial's proof belongs to the approved product studied.
Sources
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1), NEJM 2021.
- STEP 1 off-treatment extension publication (regain and cardiometabolic reversion).
- SELECT cardiovascular-outcomes trial; SURMOUNT-5 head-to-head for era context.
- Wegovy prescribing information; audited pricing — the open dataset, 2026-08-14.