Semaglutide's Heart Benefit Did Not Track Weight Loss

In SELECT, a trial of 17,604 adults with established cardiovascular disease and no diabetes, semaglutide reduced major adverse cardiac events. A prespecified analysis published in The Lancet in November 2025 found that the benefit was independent of how much weight anyone actually lost. The trial was funded by Novo Nordisk, semaglutide’s manufacturer.

Does weight loss explain semaglutide’s cardiovascular benefit?

Largely, no. Deanfield and colleagues analysed outcomes across baseline body weight, baseline waist circumference, and the change in both during treatment. Event reduction held across every category. Reductions in waist circumference were associated with cardiovascular benefit, but explained only a minority of the treatment effect.

The trial ran in 41 countries, enrolled adults aged 45 and over with a BMI of 27 or higher and prior heart attack, stroke or peripheral artery disease, and followed them for a mean of 39.8 months. The authors concluded that the cardioprotective effects extend beyond adiposity reduction, and suggested these drugs be reconceptualised as disease-modifying rather than as weight or glucose medications.

This is a randomised controlled trial, so the causal claim is solid. What remains open is mechanism: the analysis establishes that weight change is not the pathway, without establishing what is.

What else does GLP-1 do besides regulate blood sugar?

GLP-1 receptors are not confined to the pancreas. A 2024 review in Maturitas by Chavda and colleagues catalogues receptor activity affecting mitochondrial function, cellular stress resistance, inflammation and neuronal protection, and argues the hormone touches several pathways associated with biological aging. That review is narrative rather than experimental, and the lifespan-extension results it cites come from model organisms, not people.

The SELECT baseline data hints at one candidate. Inflammatory burden, measured as high-sensitivity C-reactive protein at or above 2.0 mg/L, rose from 36.4% of participants in the lowest BMI category to 72.0% in the highest. Body weight and inflammation move together at a population level, but they are not the same measurement, and one of them is far more rarely checked.

The bottom line

• Across 17,604 participants in SELECT, cardiac event reduction was independent of baseline adiposity and of the magnitude of weight loss.
• Waist circumference change was associated with benefit but accounted for only a minority of the effect.
• Body weight and inflammatory markers such as hs-CRP track each other loosely, which makes weight alone an incomplete picture of cardiometabolic risk.