The telos puts pharmacotherapy in scope because a drug is often the realistic alternative to a lifestyle change — and for the biggest lever in an obese stratum (weight), semaglutide is now the best-evidenced drug route. The SELECT trial (Lincoff, NEJM 2023) is the landmark: the first demonstration that treating obesity pharmacologically reduces hard cardiovascular events. But it proved this in one population only, and the population is not the one most of the wiki’s low-risk strata belong to. Both halves of that sentence are the finding.
What SELECT proved, and the population it proved it in
A single large event-driven RCT (n=17,604), on top of standard secondary-prevention care (90% on statins, 86% on antiplatelets):
primary MACE (CV death, non-fatal MI, non-fatal stroke): «569 of the 8803 patients (6.5%)» on semaglutide vs «701 of the 8801 patients (8.0%)» on placebo — «hazard ratio, 0.80; 95% confidence interval, 0.72 to 0.90; P<0.001», a reduction «by 20%» over a mean 39.8 months.
Absolute risk reduction is 1.5 percentage points over ~3.3 years -> NNT ~67 (inferred from Lincoff et al., 2023). That is a real, incremental benefit on top of guideline therapy — not instead of it.
Who was enrolled fixes what the number means: «patients 45 years of age or older who had preexisting cardiovascular disease and a body-mass index… of 27 or greater but no history of diabetes». This is a secondary-prevention population (prior MI, stroke, or symptomatic PAD), non-diabetic, with a placebo event rate of 8% over 3.3 years (~2.4%/yr).
The primary-prevention gap — stated by the trialists themselves
This is the load-bearing limit, and it is not the wiki’s inference — it is the paper’s own:
«An important limitation of this trial is that we included only patients with preexisting cardiovascular disease. The effects of semaglutide on primary prevention of cardiovascular events in persons with overweight or obesity but without previous atherosclerotic disease were not studied.»
So for an obese person without established atherosclerotic disease — low 10-year risk, or a zero coronary-calcium score — the hard-outcome benefit of semaglutide is not proven. This is the insufficient-evidence state, not the no-effect state (the two are kept distinct): SELECT gives no reason to think the drug stops working in primary prevention, only that it was never tested there.
The two trials bracket the hole precisely. STEP-1 (Wilding et al., 2021) is a primary-prevention population (no CVD required) — but its endpoint is weight and cardiometabolic surrogates, not events. SELECT is a hard-outcome trial — but only in secondary prevention. So: primary prevention has strong surrogate evidence and zero hard-outcome evidence; secondary prevention has the hard-outcome evidence. No trial delivers a hard-outcome benefit in primary prevention — the gap is not for want of looking at the drug, it is that the one relevant question has never been the endpoint of a trial in this population.
Two reasons the benefit would be smaller there even if the relative effect transported — see Baseline Risk and the Relative-Absolute Split and SCORE2 Baseline Risk and the ESC Treatment Thresholds:
- Absolute benefit scales with baseline risk. A primary-prevention person at, say, 5% 10-year risk (~0.5%/yr) sits roughly 5x below SELECT’s placebo event rate. Apply the same HR 0.80 and the absolute reduction shrinks ~5-fold — from ~1.5 pp/3.3 yr toward a fraction of a percentage point. The relative effect is the fragile assumption; the absolute one is small by construction.
- The relative effect itself may not transport. Mechanism (plaque already present vs not) differs between secondary and primary prevention; SELECT cannot speak to it.
Confirmed vs widely-repeated — the hierarchical-testing catch
Only the primary composite is a confirmatory result. The pre-specified gatekeeping hierarchy tested CV death next — «hazard ratio, 0.85; 95% CI, 0.71 to 1.01; P = 0.07» — which failed the gate, so «superiority testing was not performed for the remaining confirmatory secondary end points». Everything downstream is a point estimate, not a confirmed effect:
- All-cause mortality «0.81 (0.71 to 0.93)» and heart-failure composite «0.82 (0.71 to 0.96)» — directionally favourable, statistically non-confirmatory. Semaglutide reduces mortality is a common but unlicensed reading of this trial.
- Non-fatal stroke «0.93 (0.74 to 1.15)» — not reduced. (An aggregator SR of this literature was seen reporting stroke as the strongest effect; reading the trial contradicts it.)
- Non-fatal MI «0.72 (0.61 to 0.85)» and coronary revascularization «0.77 (0.68 to 0.87)» carry most of the composite.
Weight loss: the drug route to the biggest lever
body weight «-9.39» % vs «-0.88» % (difference «-8.51 (-8.75 to -8.27)» percentage points at week 104); waist circumference difference «-6.53» cm.
~9% weight loss is the mechanism-adjacent reason this matters for Fatty Liver MASLD and Weight Loss and for Layer 1 - Ranking Interventions for a Stratum: it is a pharmacological route to the same weight lever a lifestyle programme targets. The trialists note that prior non-surgical approaches reached weight loss «substantially lower than the mean 9.4% decrease observed with semaglutide» and had «uniformly failed» to move CV outcomes — so the drug is not just another weight intervention, it is the first to clear the bar. The drug and the lifestyle change are not either/or — same lever, different route, combinable.
STEP-1: the primary-prevention arm — a bigger number, on a surrogate
SELECT’s 9.4% was measured in an older, established-CVD population. STEP-1 (Wilding, NEJM 2021) ran the same drug in the population the wiki’s obese strata actually resemble — «a body-mass index… of 30 or greater (≥27 in persons with ≥1 weight-related coexisting condition), who did not have diabetes», mean age 46, ~60% at BMI ≥35, only 2.5% with coronary artery disease — i.e. essentially primary prevention, as an adjunct to lifestyle (a 500-kcal deficit plus 150 min/week of activity). Its coprimary endpoint is weight, a surrogate, not events.
mean body-weight change to week 68: «−14.9%» vs «−2.4%», difference «−12.4 percentage points» (95% CI −13.4 to −11.5); responders losing ≥10%: «69.1%» vs «12.0%»; ≥15%: «50.5%» vs «4.9%»; ≥20%: «32.0%» vs «1.7%».
Half the treated group lost ≥15% and a third lost ≥20% — the latter «approaching that reported 1 to 3 years after bariatric surgery». Waist fell «–9.42 cm» placebo-adjusted, SBP «–5.10» mmHg, CRP more than halved, and fat mass fell more than lean mass.
Do NOT read the 14.9% (STEP-1) vs 9.4% (SELECT) gap as the drug works better in primary prevention. The two trials differ on exactly the axes that move weight response, so the comparison is confounded:
| Parameter | SELECT (Lincoff 2023) | STEP-1 (Wilding 2021) | Same quantity? |
|---|---|---|---|
| Mean % body-weight change (treatment-policy, ITT) | «−9.39%» | «−14.85%» | Yes — same construct |
| Follow-up at measurement | week 104 | week 68 | No — different window |
| Population | established CVD, age 61.6, 72% male | no CVD required, age 46, 74% female | No — older/sicker vs younger |
The honest read is ~15% in a primary-prevention obese adult, ~9% in an older secondary-prevention one — a population-and-window difference, not evidence of a prevention-setting effect on the drug.
Benefit separated «early after the initiation of treatment», before much weight was lost, so «more rapid treatment-induced physiological changes beyond the magnitude of body-weight loss may have mediated at least part of the cardiovascular benefit» — SBP fell «-3.31» mmHg and hsCRP «-37.82» % on top of high statin use. Mechanism is explicitly speculative in the source; do not treat any one surrogate as the transmission channel.
The adherence cost is part of the effect
An intervention not taken has no effect, and semaglutide has a real tolerability tax:
AE-driven discontinuation «1461 patients (16.6%)» vs «718 patients (8.2%)» (P<0.001), predominantly gastrointestinal («880 patients (10.0%)» vs «172 patients (2.0%)»).
Counter-weight: serious adverse events were lower on semaglutide («33.4%» vs «36.4%»). And the weight benefit reverses on stopping — so this is a sustained commitment, the same return-on-investment framing Lifetime Benefit - The Frame for Younger Adults attaches to lifelong preventive therapy: a longer horizon is a longer treatment duration, not only a larger gain.
Durability — two-thirds of the loss returns within a year off the drug
Reverses on stopping is not a hedge; the STEP-1 off-treatment extension quantifies it. When both semaglutide 2.4 mg AND the lifestyle programme were stopped at week 68, participants «regained a mean of 11.6 percentage points (SD: 7.7) of body weight in the semaglutide arm versus 1.9 percentage points (SD: 4.8) in the placebo arm» over the following year — i.e. «participants regained two-thirds of their prior weight loss, with similar changes in cardiometabolic variables» (Wilding et al., 2022).
| Parameter (extension analysis set) | Week 68 (end of treatment) | Week 120 (1 yr off) | Same quantity? |
|---|---|---|---|
| Mean % body-weight change from baseline (sema) | «17.3%» loss | net «5.6%» loss | Yes — same construct, different timepoint |
| Regain over the off-treatment year (sema) | — | «11.6 percentage points» (≈2/3 of loss) | Yes |
| Holding ≥5% loss from baseline (sema) | 86.4% | «48.2%» | Yes — same threshold |
Cardiometabolic gains reverted too: «Cardiometabolic improvements seen from week 0 to week 68 with semaglutide reverted towards baseline at week 120 for most variables» (SBP/DBP back to baseline; CRP, HbA1c, lipids drifted back with only a small residual advantage) — and the trialists conclude «ongoing treatment is required to maintain improvements in weight and health» (Wilding et al., 2022). Two decision consequences:
- Adherence is the effect, over years not months. A GLP-1 course is not a one-time correction that banks a permanent gain; it is a maintained state whose benefit decays on the timescale of stopping. The realistic comparator to a lifestyle change must price lifelong cost, tolerability and reversibility.
- The regain is defended physiology, not relapse of resolve -> Weight-Loss Maintenance and Metabolic Adaptation: removing the exogenous satiety signal lets the post-loss appetite-hormone deficit reassert — the same mechanism that makes unaided lifestyle maintenance fail. Note the caveat the source itself flags: the extension also withdrew the lifestyle support (unlike STEP-4, which kept it), so part of the rapid regain is the loss of both props, not the drug alone.
Diabetes prevention — a secondary signal that fits the prediabetic stratum
Two-thirds of SELECT was prediabetic. Progression to diabetes was cut sharply: progression to HbA1c >=6.5% «0.27 (0.24 to 0.31)». STEP-1 shows the same in its younger primary-prevention population: among prediabetics, «84.1%» on semaglutide reverted to normoglycemia by week 68 vs «47.8%» on placebo. For an obese, impaired-fasting-glucose person this is a distinct, plausibly-relevant benefit — though on a surrogate (glycemic threshold), not a patient-important outcome, and whether it lowers hard diabetes-related outcomes in primary prevention inherits the same caveat.
Tirzepatide (SURMOUNT-1) — the class efficacy high-water, but surrogate-only and CV-untested
The best-evidenced drug on this page is semaglutide, but it is no longer the strongest weight lever. Tirzepatide — a dual GIP/GLP-1 receptor agonist — takes off more weight than any prior non-surgical agent. SURMOUNT-1 (Jastreboff, NEJM 2022) is its pivotal obesity RCT: n=2539 adults with a BMI «of 30 or more, or 27 or more and at least one weight-re- lated complication, excluding diabetes», once-weekly SC 5/10/15 mg vs placebo for 72 weeks. This is the same primary-prevention, non-diabetic obese population class as STEP-1 (mean age 44.9, BMI 38.0, no CVD required) — the population most of the wiki’s obese strata resemble.
Exposure distinction — do NOT pool it under “GLP-1”. Tirzepatide adds a second receptor axis rather than intensifying GLP-1 agonism: «the affinity of tirzepatide for GIP receptors was equal to the affinity of native GIP for GIP recep- tors, whereas tirzepatide bound GLP-1 receptors with affinity approximately five times weaker than native GLP-1». It is a related-but-different exposure from semaglutide — the isolate/food-category discipline (Is the Food Category Doing Any Work) applies to drug class too. So the page’s standing caution — do not generalize «GLP-1 class reduces CV events» from one agent — is now doubly warranted: tirzepatide differs in receptor target and has no CV trial.
The magnitude (weight, a surrogate). Treatment-regimen estimand: «−15.0%», «−19.5%», «−20.9%» (5/10/15 mg) vs «−3.1%» placebo; placebo-adjusted «−11.9 per- centage points» (5 mg) to «−17.8 percentage points» (15 mg). As-intended (efficacy estimand) absolute loss: «16.1 kg», «22.2 kg», «23.6 kg». Categorical: «50%» and «57%» of participants (10/15 mg) «had a reduction in body weight of 20% or more, as compared with 3%» placebo; exploratory ≥25% reached «36.2%» at 15 mg — «bariatric surgery re- sults in weight reduction of approximately 25 to 30% at 1 to 2 years», so the top dose approaches the surgical range on the surrogate.
Cross-trial vs semaglutide — the paper bars a direct comparison, and so do we. SURMOUNT-1’s discussion states the honest limit explicitly:
| Parameter | Tirzepatide (SURMOUNT-1, Jastreboff) | Semaglutide 2.4 mg (STEP-1, Wilding; incl. Jastreboff’s own citation) | Same quantity? |
|---|---|---|---|
| Population | BMI≥30/≥27+complication, non-diabetic, age 44.9 | BMI≥30/≥27+complication, non-diabetic, age 46 | Yes — same class |
| Endpoint | body weight (surrogate), wk 72 | body weight (surrogate), wk 68 | Yes construct; ~same window |
| Placebo-adjusted weight, lowest dose | 5 mg «11.9%» | 2.4 mg «12.4%» | Yes construct; cross-trial |
| Placebo-adjusted weight, top dose | 15 mg «−17.8 percentage points» | 2.4 mg «−12.4 percentage points» (STEP-1, on this page) | Yes construct; cross-trial |
| ≥20% responders | 57% (15 mg) | 32.0% (STEP-1) | Yes construct; cross-trial |
| Hard CV-outcome evidence | none (weight endpoint; MACE only as adjudicated safety AE, 4/5/0 vs 5 placebo — tiny, not powered) | none in STEP-1 — SELECT supplies it separately | G-gap, not a value |
The source’s own words: «It is impor- tant to note that no direct comparison of these trials can be made, since trial populations and designs differed.» Even so, tirzepatide’s lowest dose (placebo-adjusted 11.9%) already ≈ semaglutide’s full effect (12.4%), and the top dose roughly doubles it — a real efficacy gap on the surrogate, quoted here as a cross-trial contrast in a matched population class, not as a head-to-head (the obesity head-to-head does not exist; SURPASS-2 was in T2D and is not held).
The load-bearing limit — bigger surrogate does NOT license a bigger (or any) CV claim. SURMOUNT-1’s primary endpoint is body weight, a surrogate (Surrogate Outcomes); the causal transmission from weight to patient-important CV events is a separate evidenced step, and for tirzepatide that step has never been trialled. The SELECT-equivalent hard-outcome trial does not exist: — the tirzepatide morbidity-mortality CV outcome trial; when it lands it either extends the SELECT hard-outcome finding to the dual agonist or does not. This is the insufficient-evidence state, not no-effect. And the surrogate-to-outcome gap is not hypothetical: Does Weight Loss Reduce Cardiovascular Events holds the worked case where a large weight/CRP/BP surrogate improvement (Look AHEAD) bought no measurable CV-event reduction — so a record-breaking weight number is exactly the place to not assume the hard outcome follows.
Tolerability + adherence (layer 3), consistent with the class. «The most common adverse events with tirzepatide were gastrointestinal, and most were mild to moderate in severity, occurring primarily during dose escalation»; AE-driven discontinuation «4.3%, 7.1%, 6.2%, and 2.6%» (5/10/15 mg / placebo) — the same GI tolerability tax carried above for semaglutide and corroborated at umbrella grade on GLP-1 Non-Cardiometabolic Effects and Safety. The 72-week duration «enabled par- ticipants to reach a weight plateau in the 5-mg group and near-plateaus in the 10-mg and 15-mg groups» — the effect is a maintained state on chronic drug, not a one-time correction; like semaglutide, the realistic comparator to a lifestyle change must price in lifelong adherence, cost, and reversibility on stopping.
Decision relevance (tirzepatide). For an obese, non-diabetic, primary-prevention adult, tirzepatide is the strongest available weight lever short of surgery — ~15-21% loss by dose, half losing ≥20% at the top dose — but rank it, like semaglutide there, on the weight/cardiometabolic-surrogate lever and its downstream (MASLD, diabetes prevention, function), not on a promised CV-event reduction, which is unproven for this agent. Against semaglutide it offers more weight loss but less outcome evidence (no CV trial) — a genuine surrogate-vs-outcome trade the person weighs at layer 3.
(inferred from Jastreboff et al., 2022; Lincoff et al., 2023; Wilding et al., 2021)
Provenance and limits
- Industry origin: both trials were «Funded by Novo Nordisk» and sponsor-designed («The sponsor (Novo Nordisk) designed the trial and oversaw its conduct» — STEP-1). A COI flag on both, not a refutation — but the symmetric-standards rule applies, and two sponsor-run trials are not two independent lines of evidence.
- Two trials, one drug, one sponsor. SELECT + STEP-1 are both semaglutide 2.4 mg. Tirzepatide (dual GIP/GLP-1 agonist, ~15-21% weight loss — larger than semaglutide) has no dedicated CV-outcome trial (SURMOUNT-1 is weight-surrogate only — see the tirzepatide section above); oral formulations are not here. Do not generalize GLP-1 class reduces CV events in obesity from one agent — the larger weight loss of the dual agonist does not carry the CV benefit with it.
- Net-safety direction is population-dependent, not a contradiction. Serious AEs were lower on semaglutide in SELECT («33.4%» vs «36.4%») but higher in STEP-1 («9.8%» vs «6.4%»). Not a tension: SELECT’s established-CVD patients carry a high background serious-event rate the drug’s CV benefit offsets, whereas STEP-1’s healthy population has little to offset, so the drug’s own GI/hepatobiliary serious events dominate. The GI tolerability tax is consistent across both (discontinuation «7.0%» vs «3.1%» in STEP-1).
- Narrow demographics: SELECT 27.7% women / 3.8% Black; STEP-1 «preponderance of women and White participants» and «relatively short duration».
- Cross-population comparison is not confirmation: the T2D GLP-1 meta-analysis the discussion cites (Sattar 2021, «0.86; 95% CI, 0.80 to 0.93») is a different population reaching a similar HR — an echo, not independent backing of the obesity result (and Sattar is not held here). Its successor now IS held — the class CVOT+renal meta-analysis (Badve 2024, 11 trials) updates Sattar 2021 and holds the class-level pooled evidence on GLP-1 Receptor Agonists and Cardiovascular and Kidney Outcomes: the GLP-1 class cuts MACE «HR 0·87, 95% CI 0·81 to 0·93» and all-cause death «HR 0·88, 95% CI 0·83 to 0·93» (high-certainty), consistent regardless of diabetes status (p-heterogeneity vs SELECT 0·24 for MACE) (Badve et al., 2025). This still is not type-E independent backing of SELECT — Badve pools SELECT itself and shares its co-author Colhoun — so it is class-level refinement (F), not corroboration by a separate route. What it changes: SELECT is no longer the lone hard-outcome GLP-1 trial the wiki holds; the class effect is robust, but SELECT remains the only non-diabetic trial in the pool, so the primary-prevention gap this page centres is intact.
(inferred from Lincoff et al., 2023; Wilding et al., 2021)
Decision relevance
- Obese + established CVD + non-diabetic: semaglutide is a strong incremental option — NNT ~67 for MACE over ~3.3 years, on top of statins/antiplatelets, with a net-favourable serious-AE profile.
- Obese + primary prevention (low 10-year risk, CAC=0): the hard-outcome benefit is unproven and would be small in absolute terms even if it transported. What is well-evidenced there (STEP-1) is large and reliable: ~15% weight loss (half lose ≥15%), waist/BP/CRP improvement, and diabetes prevention (84% revert from prediabetes) — all real, all surrogate. Rank the drug for such a person on the weight lever and diabetes prevention, not on a promised CV-event reduction.
- Against lifestyle: not a substitution question with a fixed answer — same lever, and the swing factors are adherence, cost, GI tolerability, and reversibility on stopping, all elicited at layer 3.
(inferred from Lincoff et al., 2023; Wilding et al., 2021)
The non-cardiometabolic ledger has its own home
The CV/weight case above is only half the drug decision; the non-cardiometabolic effects and harms (GI events, cancer signals, pancreatitis, fracture, dementia, infections) are graded on a gold-tier umbrella of 60 meta-analyses and held on GLP-1 Non-Cardiometabolic Effects and Safety. Three findings there bear directly on this page’s decision:
- the GI tolerability tax carried above (STEP-1 discontinuation) is corroborated at umbrella grade — nausea OR 2.47, vomiting OR 2.78, diarrhea OR 1.94 (Yang et al., 2026);
- the rodent thyroid-C-cell concern shows no robust human signal (thyroid cancer OR 1.43, 0.95-2.13, NS), confirming the transportability read used here (Yang et al., 2026);
- a protective fracture signal (OR 0.67, 0.52-0.87) partly offsets the sarcopenia/fall worry that rapid weight loss otherwise raises (Yang et al., 2026).
Most other non-cardiometabolic signals are exploratory (single-trial-fragile), so they refine rather than reverse the net-benefit picture above.
The cross-drug placement — sole hard-outcome drug, but the signal is this page’s own trials [2026-08-22, Nong]
A 19-drug network meta-analysis (Nong 2026; 262 RCTs) places SELECT’s finding in the whole anti-obesity class, and the placement is the value: subcutaneous semaglutide is «the only drug associated with reduced all cause mortality (risk ratio 0.81, 95% confidence interval 0.72 to 0.93) and myocardial infarction (0.72, 0.61 to 0.85)», adding heart failure (0.43, 0.21-0.84) and probable kidney disease progression (0.80, 0.65-0.98, moderate) (Nong et al., 2026). Tirzepatide — the larger weight lever above — reaches only heart-failure signals, no mortality/MI. So across the class, the biggest weight loss is not the drug with the hard-outcome evidence -> Comparing Obesity Drugs.
But this is F-refinement, NOT independent (type-E) corroboration, and the numbers prove it. The NMA’s
mortality/MI estimates are «largely informed by cardiovascular outcome trials in high risk populations»
(Nong et al., 2026) — i.e. SELECT and kin,
already held here — and the pooled figures are near-identical to SELECT’s own (all-cause death RR 0.81 vs
HR 0.81; MI RR 0.72 vs HR 0.72). The NMA re-pools SELECT, it does not reach the finding by a separate
route, so no [E-independent] is claimed and the SELECT within-trial caveats above still stand (the
hierarchical-gate non-confirmation of all-cause mortality is a fact about SELECT’s statistics; the NMA’s
«high certainty» is a meta-analytic pooling across the same CV-outcome-trial base, and inherits the same
high-CV-risk-population restriction). The primary-prevention gap this page centres is therefore intact:
the mortality signal remains a route-(a) finding concentrated where CV risk is highest.
(inferred from Nong et al., 2026)
Gaps this opens
- No primary-prevention CV-outcome trial for any obesity drug — the single largest hole for applying this to a low-risk stratum. G.
- No head-to-head of drug vs sustained lifestyle vs bariatric surgery on hard outcomes.
- Weight loss on hard outcomes as an exposure in its own right (independent of the drug) is still unheld -> Weight Loss and Mortality (a future page, not yet a held source).