Semaglutide extended median lifespan from 742 to 834 days in 20-month-old female C57BL/6 mice, according to a study published September 2 in Nature. The lifespan arm included 79 mice treated daily with subcutaneous semaglutide or saline until death, while separate cohorts were used to test physiological function, molecular aging markers, and a direct comparison with 24% calorie restriction.
The experiment started semaglutide late in life and followed one cohort until death
Researchers led by Danica Chen at the University of California, Berkeley used 20-month-old female C57BL/6 mice, an age at which aging-related physiological decline is already established. The animals received 10 nanomoles per kilogram of semaglutide by subcutaneous injection once daily. In the lifespan experiment, 39 mice received saline and 40 received semaglutide for the remainder of life.
The design matters because the intervention did not begin in young animals. The investigators were asking whether glucagon-like peptide-1 (GLP-1) receptor activation could alter aging trajectories when treatment started late in life, rather than whether lifelong exposure could prevent aging from developing. Semaglutide reduced food intake by 24%, and body-weight loss was driven predominantly by lower fat mass.
Separate animals were treated for three months for functional, cellular, and molecular measurements. Physiological testing used 10 mice per group, while neural stem-cell and other molecular analyses used cohorts of five or six mice per group.
Lifespan increased while several measures of physical and cognitive function improved
Median lifespan was 742 days in control mice and 834 days in semaglutide-treated mice, a difference of 92 days. The distribution of recorded endpoint categories did not differ significantly between groups, while age at death appeared delayed across several non-tumor categories.
After three months of treatment, semaglutide-treated mice also performed better on several measures of movement, muscle function, spatial memory, and glucose tolerance. The paper reports improvements across rotarod, inverted-screen, treadmill, Barnes-maze, and glucose-tolerance testing.
These results extend a broader question already raised by human research on this drug class: why do GLP-1 medicines show effects across so many organ systems? Bites of Bio’s review of GLP-1 drugs beyond weight loss summarizes cardiovascular, kidney, liver, and sleep-apnea evidence in humans. The mouse study does not prove that aging is the common mechanism behind those benefits, but it gives that hypothesis a testable biological framework.
The drug reproduced much of calorie restriction but not all of it
Because semaglutide reduced food intake, the researchers needed to separate drug effects from the known effects of eating fewer calories. In a separate five-month longitudinal experiment, 10 mice per group received saline, semaglutide, or a 24% calorie-restricted diet matched to the reduction in food intake produced by semaglutide.
Many outcomes moved similarly with semaglutide and calorie restriction. Both interventions attenuated age-associated decline in several physiological measures, and gene-expression patterns overlapped in pathways involving inflammation, lipid metabolism, adaptive immunity, glucose and insulin responses, and protein quality control.
The two interventions were not identical. Calorie-restricted mice consumed their food rapidly and then underwent a prolonged fasting period, while semaglutide-treated mice ate more gradually. Semaglutide also produced more favorable trajectories than calorie restriction in exploratory behavior, spatial memory, and glucose control. Chen said, “These differences point to the possibility that GLP-1 drugs tap into a biological pathway independent of calorie restriction.”
That interpretation remains a hypothesis rather than a demonstrated separate pathway. The direct comparison was small, and the investigators did not identify a single mechanism that explains the differences.
Molecular changes touched several recognized hallmarks of aging
The researchers examined tissues from the liver, muscle, brain, spleen, kidney, bone marrow, and adipose tissue. Semaglutide altered measures linked to several recognized hallmarks of aging, including inflammation, cellular senescence, genomic instability, mitochondrial dysfunction, loss of protein homeostasis, and stem-cell decline.
The treatment also increased nicotinamide adenine dinucleotide levels, induced several sirtuin genes, reduced insulin-like growth factor 1, and altered transcriptional programs linked to nutrient sensing and longevity. In the hippocampus, treated mice had higher measures of neural stem-cell activity and neurogenesis.
These molecular results fit with an earlier Bites of Bio explainer on the metabolism-aging link: nutrient sensing and energy balance intersect with pathways that regulate cellular maintenance. They do not establish that semaglutide converted a mouse into a biologically younger animal. The experiments measured selected molecular and physiological markers, not a single validated biological-age endpoint.
What the evidence cannot yet answer
The biggest limitation is species. This was a mouse study using one inbred strain, and the lifespan experiment included only female animals. The authors selected females to reduce confounding from male aggression and injury in long-term housing, but that choice means the survival result has not been shown in male mice.
The dosing regimen also limits translation. Mice received 10 nanomoles per kilogram every day by injection, and the experimental regimen should not be converted into an anti-aging dose for people. The study was designed to test biology in mice, not to establish a human treatment schedule.
The study also cannot show whether semaglutide extends human lifespan. Its authors explicitly state that determining whether GLP-1 receptor activation changes aging trajectories and lifespan in humans will require long-term clinical studies designed around aging-related outcomes. Existing human benefits of the drug class should not be reinterpreted as proof of a longevity effect.
Funding was public, but the university has filed a related patent
The work was supported by National Institute on Aging grants R01AG063404, R01AG063389, and R01AG082105, along with support from the National Institute of Food and Agriculture. The paper also discloses that the Regents of the University of California filed a patent application related to GLP-1 receptor agonists for healthy aging.
That conflict does not change the experimental results, but it is relevant when claims about future longevity applications are interpreted. The strongest conclusion remains narrow: in older female C57BL/6 mice, late-life semaglutide treatment extended median lifespan and improved multiple measures associated with aging.
References
- Feng Y, Barthez M, Wang Y, et al. Late-life semaglutide treatment slows ageing and extends lifespan in female mice. Nature. 2026. DOI: 10.1038/s41586-026-10940-7.
- National Institutes of Health. GLP-1 treatment late in life extends lifespan in animal model. September 2, 2026. NIH news release.