Nature reports late-life semaglutide extended lifespan 12% in female mice

Researchers at the University of California, Berkeley reported on September 2, 2026 that semaglutide, started late in life, slowed measures of aging and extended lifespan in female mice ^[1][2]. The National Institutes of Health, which funded the work through the National Institute on Aging, said mice treated until the end of life had a median lifespan nearly 100 days longer than untreated mice ^[2]. In the paper, that works out to a rise in median lifespan from 742 to 834 days, roughly 12% ^[1].

What the study did

The team, led by Danica Chen, Ph.D., a professor of metabolic biology and nutrition at UC Berkeley, gave daily subcutaneous semaglutide or a vehicle injection to 20-month-old female C57BL/6 mice ^[1][2]. One cohort was treated for three months for physiological, molecular and cellular tests; a separate cohort stayed on treatment for the rest of their lives for the lifespan analysis ^[1]. Twenty months in a mouse is late middle age to early old age; the researchers chose it to test the drug "at a time when the effects of aging are most pronounced" ^[2].

Treated mice ate 24% less food ^[1]. They lost weight, and the loss came mostly from fat: the share of body weight from white adipose tissue fell, while the percentage of lean mass rose ^[1]. After adjusting for body weight, the drug did not significantly change locomotor activity, respiratory exchange ratio, oxygen consumption, carbon dioxide production or energy expenditure ^[1].

Compared with controls, treated mice showed better muscle and cognitive function, and gene expression analysis showed reductions in hallmarks of aging such as increased inflammation and reduced regenerative capacity ^[2].

Semaglutide versus eating less

The more unusual part of the study was a head-to-head comparison. Over five months, one group of 20-month-old female mice got semaglutide while another was fed a 24% calorie-restricted diet matched to the treated animals' feeding pattern ^[2]. Calorie restriction is the best-established way to slow aging in animals, but it is hard to sustain, which is why scientists look for drugs that mimic it ^[1].

The two groups looked similar on many measures, with most physiological readings holding steady ^[2]. But semaglutide-treated mice went above their own starting levels in exploratory behavior, spatial memory and blood-sugar maintenance, and had more favorable trajectories than the calorie-restricted animals on those measures ^[1][2]. Metabolic rate fell in the calorie-restricted mice but was largely unchanged with semaglutide ^[2].

"These differences point to the possibility that GLP-1 drugs tap into a biological pathway independent of calorie restriction," Chen said, calling that pathway "an important direction for future research" ^[2].

Rafael de Cabo, Ph.D., a senior investigator at NIA who wrote a commentary on the study, framed the bigger idea this way: "Most chronic diseases are deeply rooted in the aging process. If GLP-1 agonists do indeed slow it down, then a wide range of clinical benefits is exactly what you'd expect to see" ^[2].

Why it matters for patients

This is a mouse study, and NIH said plainly that the findings "do not imply that similar results could be achieved immediately in humans" ^[2]. The work does offer a possible explanation for why semaglutide has shown benefits in so many different organs in human trials, including heart, kidney and liver disease ^[1]. But an explanation is not proof, and a longer life in mice is not evidence that any GLP-1 drug extends human life.

Several limits are worth noting. Only female mice were studied, so the sources do not say whether male mice would respond the same way ^[1][2]. The animals were healthy older mice, not people with obesity or diabetes, and dosing was a daily injection in mice rather than the weekly regimens used in humans ^[1]. Effects of calorie restriction itself vary by sex, strain, age and health status ^[1].

What happens next

The paper was published in Nature on September 2, 2026 ^[2]. NIH said additional clinical work will be needed to judge any effect on human longevity, pointing to a recent post-hoc analysis of the SLIM LIVER trial as an example ^[2]. Chen said future clinical investigations may also look at healthy older adults ^[2]. No such longevity trial, timeline or sponsor is named in these sources, so when or whether one starts is not yet known.