Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)

SURMOUNT-1 demonstrated weight loss with a medication that approaches what was once achievable only with surgery — a development with major implications for cardiovascular risk.

In people with obesity but without diabetes, tirzepatide (a dual GIP/GLP-1 receptor agonist) produced up to about 21 percent body-weight reduction at the highest dose over the trial, alongside improvements in blood pressure, lipids, and other cardiometabolic markers. The magnitude was unprecedented for a drug.

Obesity drives hypertension, diabetes, and dyslipidemia — the engines of atherosclerosis — so a therapy that reliably produces large, sustained weight loss is potentially transformative for prevention. The caveat for this trial is that its endpoint was weight and metabolic markers, not cardiovascular events; whether the benefits translate into fewer heart attacks awaits dedicated outcomes trials (now underway for this drug class).

We rate the evidence strong. It is a large, rigorous randomized trial establishing a powerful effect on weight and cardiometabolic risk factors, with the standard caveat that surrogate improvements must still be confirmed to reduce hard cardiovascular outcomes.