What the outcome trials show for semaglutide and tirzepatide across the heart, kidneys, liver, lungs and joints — and why that matters for healthy aging.
Semaglutide and tirzepatide earned their approvals on weight and HbA1c. Since 2023, a run of large outcome trials has asked a harder question: do these drugs change what actually happens to patients?
The answer, across five organ systems, has been yes. In several trials the effect appeared before, or independent of, the weight loss itself.
Every result on this page comes from a randomized trial published in NEJM or Heart, most of them Phase 3, using full therapeutic doses of the FDA-approved products in defined patient populations. Phase 2 and pending-publication findings are labeled as such.
The systems where these trials found benefit are the same systems that drive age-related decline: cardiovascular events, chronic low-grade inflammation, kidney function, fatty liver disease, sleep-disordered breathing, and joint pain that limits activity. None of these trials was designed to measure lifespan, and no GLP-1 product carries a longevity indication. But two of them recorded lower all-cause mortality as a secondary finding — FLOW in kidney disease and SURPASS-CVOT in cardiovascular disease — and the inflammation data suggest a mechanism that operates on more than body weight.
That is the honest framing: these are disease-outcome results in defined populations, with a plausible and partly demonstrated reach into the biology of aging. What follows is the evidence itself.
Full dose, 2.4 mg weekly
−20%
Major cardiovascular events in adults with heart disease and overweight, without diabetes
SELECT · NEJM 2023
−38%
hsCRP vs. placebo, with reductions visible by week 4 — before meaningful weight loss
SELECT hsCRP · EAS 2024*
HFpEF
Improved symptoms, physical function and exercise capacity in obesity-related heart failure
STEP-HFpEF · NEJM 2023
−24%
Major kidney events, with slower eGFR decline in diabetes with chronic kidney disease
FLOW · NEJM 2024
MASH
Resolved steatohepatitis and improved fibrosis in Phase 3 — the first GLP-1 liver indication
ESSENCE · NEJM 2025
Knee OA
Reduced osteoarthritis pain and improved function alongside weight loss
STEP 9 · NEJM 2024
*Presented at EAS 2024 (Plutzky J, Ridker PM, et al.); final journal citation to be confirmed.
SELECT enrolled 17,604 adults with established cardiovascular disease and BMI ≥ 27 but no diabetes — a population where no weight-loss drug had ever shown an outcome benefit. Over a mean follow-up of 40 months, 8.0% of the placebo group had a major adverse cardiovascular event versus 6.5% on semaglutide, a hazard ratio of 0.80 for the composite of cardiovascular death, non-fatal MI and non-fatal stroke.
The curves separated early, and the benefit was consistent across baseline weight — a signal that the mechanism is not weight loss alone. This trial is the basis of the 2024 FDA label expansion for cardiovascular risk reduction.
−38%
hsCRP vs. placebo. High-sensitivity C-reactive protein is the most widely used blood marker of systemic inflammation and an independent predictor of cardiovascular events.
In the SELECT biomarker analysis, hsCRP had already dropped by week 4, when average weight loss was still minimal. The reduction was seen across all baseline weight categories and held in patients who lost little weight.
Chronic low-grade inflammation is a shared driver of atherosclerosis, insulin resistance, MASH and age-related decline — the same conditions where the outcome trials showed benefit. This supports a direct anti-inflammatory action of GLP-1 receptor activation, in addition to the effects of fat loss.
Heart failure with preserved ejection fraction is the form most tied to aging, obesity and metabolic disease — and the hardest to treat. In STEP-HFpEF, semaglutide produced a larger improvement in the Kansas City Cardiomyopathy symptom score (+16.6 vs +8.7 points) and 6-minute walk distance (+21.5 m vs +1.2 m), with fewer heart-failure events and lower hsCRP over 52 weeks.
FLOW enrolled 3,533 people with type 2 diabetes and chronic kidney disease and was stopped early for efficacy: a 24% reduction in major kidney events (kidney failure, ≥50% eGFR loss, kidney or cardiovascular death), slower annual eGFR decline, 29% fewer major cardiovascular events and 20% lower all-cause mortality.
Metabolic dysfunction-associated steatohepatitis is the leading driver of liver disease in the metabolic population. In ESSENCE (Phase 3, 72-week biopsy analysis), steatohepatitis resolved without worsening fibrosis in 62.9% vs 34.3%, and fibrosis improved in 36.8% vs 22.4% — the basis for the first GLP-1 liver indication (FDA, 2025).
Obesity is the strongest modifiable risk factor for knee osteoarthritis, and pain is what limits activity. In STEP 9, WOMAC pain score fell 41.7 points vs 27.5 with placebo over 68 weeks, with better physical function. Weight loss explains much of the effect; a direct anti-inflammatory contribution is plausible but not proven.
Full dose, up to 15 mg weekly · Dual GIP/GLP-1 receptor agonist
−63%
Breathing interruptions in obesity-related sleep apnea; the only medication FDA-approved for OSA
SURMOUNT-OSA · NEJM 2024
Non-inferior
Matched dulaglutide on major cardiac events over 4 years, with lower all-cause mortality
SURPASS-CVOT · NEJM 2025
−38%
Cardiovascular death or worsening heart failure in obesity-related HFpEF
SUMMIT · NEJM 2025
−94%
Progression from prediabetes to type 2 diabetes over three years
SURMOUNT-1 3-yr · NEJM 2025
MASH
Steatohepatitis resolved in a majority of treated patients in Phase 2
SYNERGY-NASH · NEJM 2024
−10 mmHg
24-hour ambulatory systolic blood pressure, comparable to a first-line antihypertensive
SURMOUNT-1 ABPM · Heart 2024
SURMOUNT-OSA enrolled 469 adults with moderate-to-severe obstructive sleep apnea and obesity, studied with and without CPAP. At week 52, the apnea–hypopnea index fell by 25.3 events per hour without CPAP and 29.3 with CPAP, versus 5.3 and 5.5 on placebo — up to a 63% reduction in breathing interruptions. Oxygen desaturation, hsCRP, systolic blood pressure and sleep-related quality of life all improved. FDA approval for OSA in adults with obesity followed in December 2024, the first drug approved for the condition.
SURPASS-CVOT followed 13,299 people with type 2 diabetes and established cardiovascular disease for a median of four years, compared head-to-head against dulaglutide — an agent with proven cardiovascular benefit — rather than placebo. Tirzepatide was non-inferior on major cardiac events (HR 0.92), with lower all-cause mortality (HR 0.84) and a better composite of cardiorenal outcomes.
SUMMIT enrolled 731 patients with heart failure, preserved ejection fraction and BMI ≥ 30, followed a median of two years: a 38% reduction in the composite of cardiovascular death or worsening heart-failure event, larger gains in symptom score (+6.9 points) and 6-minute walk distance, lower hsCRP, and systolic blood pressure down about 5 mmHg.
The SURMOUNT-1 three-year extension followed 1,032 adults with obesity and prediabetes for 176 weeks on treatment, plus a 17-week off-drug period. Progression to type 2 diabetes was 1.3% on tirzepatide versus 13.3% on placebo — a hazard ratio of 0.06, a 94% reduction. Weight loss was sustained at −22.9% (pooled 10 and 15 mg) vs −2.1% on placebo. After stopping, weight and glucose partly rebounded; the effect is treatment-dependent, as with blood-pressure or lipid therapy.
SYNERGY-NASH (Phase 2) studied 190 patients with biopsy-confirmed MASH and stage 2–3 fibrosis for 52 weeks. Steatohepatitis resolved without worsening fibrosis in 44–62% across doses vs 10% on placebo. Fibrosis improvement favored tirzepatide but was not powered for significance; the Phase 3 trial (SYNERGY-OUTCOMES) is ongoing.
An ambulatory monitoring substudy of SURMOUNT-1 (494 participants, 36 weeks) — a more rigorous measure than office readings — found 24-hour systolic pressure fell 7.4 to 10.6 mmHg vs placebo across doses, comparable to a first-line antihypertensive. The effect was largely, but not entirely, explained by weight loss.
| Outcome | Semaglutide | Tirzepatide |
|---|---|---|
| Major cardiovascular events | −20% vs placebo (SELECT, Phase 3) | Non-inferior to dulaglutide; lower mortality (SURPASS-CVOT, Phase 3) |
| Heart failure (HFpEF) | Symptoms, function, exercise capacity (STEP-HFpEF) | −38% CV death or worsening HF (SUMMIT) |
| Inflammation (hsCRP) | −38%, by week 4 (SELECT analysis) | Reduced in SUMMIT and SURMOUNT-OSA |
| Kidney | −24% major kidney events (FLOW, Phase 3) | Cardiorenal composite improved (SURPASS-CVOT) |
| Liver (MASH) | Phase 3 — approved indication (ESSENCE) | Phase 2 (SYNERGY-NASH); Phase 3 ongoing |
| Sleep apnea | — | −63% AHI; approved indication (SURMOUNT-OSA) |
| Diabetes prevention | — | −94% progression over 3 years (SURMOUNT-1) |
| Blood pressure | Reduced (STEP program) | −10 mmHg 24-h systolic (SURMOUNT-1 ABPM) |
| Knee osteoarthritis | Pain and function (STEP 9) | — |
Trial names refer to the branded products at full therapeutic dose. "—" means no dedicated outcome trial has been published, not evidence of no effect.
Every trial used Wegovy, Ozempic, Zepbound or Mounjaro at therapeutic doses. Compounded semaglutide and tirzepatide are not FDA-approved and have not been evaluated by FDA for safety, effectiveness or quality. The data describe the molecules in those trials, not any compounded product.
Outcome benefits were measured at full dose in defined populations. There are no published outcome data for sub-therapeutic dosing, and none of the results here should be attributed to microdose regimens.
No trial has tested whether these drugs extend lifespan or healthspan in people without the diseases studied. The all-cause mortality signals in FLOW and SURPASS-CVOT were secondary findings in high-risk populations.
Cognition is not a supported benefit: the EVOKE oral semaglutide trials in Alzheimer's disease did not meet their endpoints (2025). Tirzepatide's MASH data remain Phase 2, and the SELECT hsCRP analysis should be cited to its final journal publication.
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