Eli Lilly and Novo Nordisk both presented exploratory aging data on their GLP-1 drugs at the 2026 Aging Research and Drug Discovery meeting at Harvard, with some aging clock models estimating biological age reductions of several years after treatment. Neither company claims to have shown anything about human lifespan.

The drugs are semaglutide (sold as Ozempic and Wegovy) and tirzepatide (Mounjaro and Zepbound), the latter a dual agonist hitting both GIP and GLP-1 receptors. Aging clocks are statistical models that estimate biological age from blood biomarkers such as proteins or DNA methylation patterns, not direct measures of health.

Two companies, two kinds of clock

Novo Nordisk analyzed blood from participants across multiple Phase 3 trials using proteomic aging clocks, and reported reduced readings across several organs versus placebo. Per MIT Technology Review, some models showed differences of roughly 2 to 3 years, with heart-related protein clocks reaching about 4 years.

Lilly took a different route, comparing DNA methylation profiles in 71 SURMOUNT-5 participants before treatment and after 72 weeks. Improvement signals appeared across multiple epigenetic clocks covering heart, kidney, liver and immune markers.

The mouse lifespan result

The most direct evidence is not human. A study published in Nature in September 2026 started semaglutide in 20-month-old female mice and reported a median lifespan of 834 days in the treated group against 742 days in controls.

The authors note some effects resembled caloric restriction without simply replicating it. Extended lifespan in mice does not translate to humans, and the paper is framed as proof of concept.

Where the evidence stops

Lilly's analysis included only the tirzepatide arm, with no parallel comparison against the trial's active control, which the company says leaves the results preliminary. In Novo's data, different clock types disagreed, and overall aging clocks showed no significant change.

Most participants in this work already have obesity, diabetes or other metabolic conditions, so whether anything similar happens in metabolically healthy people is unanswered. The VITAL-H and Moody Longevity trials are now recruiting in older adults to test function, not just biomarkers.

Bottom line

The interesting question is whether a younger-looking clock reading corresponds to anything a person can feel. Nobody has shown that yet, and the companies presenting the data are not pretending otherwise.