Old Mice Lived Longer on Semaglutide

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From the Juicebox Blog · Research

Old Mice Lived Longer on Semaglutide. Look at What the Drug Copied.

A Nature study started 20-month-old female mice on daily semaglutide and they outlived the untreated mice by about 12 percent. The more interesting finding is that the drug’s fingerprint matched calorie restriction — the same fingerprint that showed up inside beta cells in a separate GLP-1 study.

Scott Benner · September 2026

Start an old mouse on semaglutide, keep it on the drug for the rest of its life, and it lives about 12 percent longer. That is the headline from a study published in Nature on September 2 by Danica Chen’s lab at the University of California, Berkeley. Median lifespan went from 742 days in the untreated mice to 834 days in the treated ones. In mouse time, that is about three months.

The mice were 20 months old when the injections started. One outside expert who reviewed the paper put that at roughly the equivalent of a 62-year-old woman. They were all female. And they ate 24 percent less than the untreated mice, which is the detail the rest of the story turns on.

Because eating 24 percent less is, on its own, a well-known way to make a mouse live longer. Researchers call it calorie restriction, and it has extended lifespan in nearly every animal it has been tried on. So the real question in this paper is not whether the mice lived longer. It is whether semaglutide did anything beyond making them eat less. The authors say it did. Here is the study, one step at a time.

The study

What the old mice went through

Tap a step. Every figure is from the Nature paper.

THE SETUP79 old mice, daily shots 3 MONTHSFunction tests THE TISSUESHallmarks of aging 5 MONTHSDrug vs. eating less LIFESPAN742 vs. 834 days

Forty 20-month-old female mice got a daily injection of semaglutide under the skin; 39 got saline. Semaglutide is the molecule in Ozempic and Wegovy. The dose was a research dose for mice, not a translation of any human prescription. In the lifespan arm the injections continued until each mouse died. Separate groups were treated for three or five months for the function and tissue studies.

What the study shows

This work was funded by the National Institute on Aging, part of the NIH, and by the National Institute of Food and Agriculture. No drug company is listed as a funder. Novo Nordisk, which makes semaglutide, is not an author or a sponsor.

On the evidence ladder this is animal research: well run, blinded where it could be, with 79 mice in the lifespan arm and 10 per group in the function arms. It shows what the drug did in old female laboratory mice of a single inbred strain. It cannot show what the drug does to a person’s lifespan, and the authors say so. Whether GLP-1 activation changes aging in humans, they write, will take long-term clinical studies designed to measure aging outcomes in older people.

The comparison to calorie restriction is where the paper earns its place, so it gets its own box.

Head to head

Semaglutide vs. eating 24 percent less

Tap a tab. A third group of mice got no drug and simply had their food cut to match what the semaglutide mice ate.

Where they matched Where the drug pulled ahead Where they differed

Now the part worth holding up against something else. A separate post on this blog covered a Salk Institute study, published in PNAS in March, that traced how a GLP-1 changes gene expression inside the beta cell. Buried in that paper was a line that was easy to pass over at the time: in mouse islets, the drug pushed beta cells toward the marker genes seen in calorie-restricted mice, and away from the ones seen in mice on a high-fat diet.

Different lab. Different organ. Different question. Same fingerprint. The Salk team was looking at one cell type in the pancreas. The Berkeley team was looking at the liver, blood, brain, and lifespan of a whole animal. Neither paper cites the other, and nothing in either one proves they are describing the same mechanism. That connection is an editorial observation, not a finding. But when two groups studying GLP-1 signaling from opposite ends both end up holding a calorie-restriction gene list, that is worth writing down.

What nobody knows yet

The paper is clear about its edges. Two of them decide how much of this transfers to anyone reading it.

OPEN QUESTION 1

Does it hold in males, or in people?

Every mouse in this study was female, chosen to avoid the fighting and injuries that complicate long-term studies in male mice. Aging differs by sex, in mice and in people. All of the mice were one inbred strain, bred for genetic uniformity, which is the opposite of a human population. On the human side, one outside expert noted that the mice started the drug at about 75 percent of their expected lifespan and stayed on it for life; for a woman in the UK that would mean starting around 62 and never stopping. Large human trials have linked GLP-1 drugs to fewer heart attacks, strokes, and deaths in people with type 2 diabetes and with obesity, but that is what those trials counted. They did not measure aging. Nobody has run the human version of this experiment.

Tap to expand ▼

OPEN QUESTION 2

Is it the drug, or is it the eating less?

The authors argue for both. Most of the benefit matched what a plain 24 percent food cut produced, which points at the calories. But three outcomes improved beyond what calorie restriction achieved, and the treated mice never went through the fasting-and-foraging rhythm that calorie restriction imposes. The authors read that as a sign that GLP-1 receptor activation taps something calorie restriction does not. An outside neuroscientist offered a simpler explanation for the brain results: the semaglutide mice moved more, and physical activity on its own is known to boost the growth of new neurons. The paper cannot settle which is right, and it does not claim to.

Tap to expand ▼

Twelve percent longer in a mouse is a result. Twelve percent longer in a person is a story until someone runs the trial.

Where this stands

What this means if you live with diabetes

The arithmetic is sitting right there and everyone is going to do it. Twelve percent of an 80-year life is nine or ten years. Nobody has earned that number. Mouse lifespan gains shrink, sometimes to nothing, on the way to people, and the mice in this study had no diabetes, no autoimmunity, and no other medications on board.

If you have type 2 diabetes and take a GLP-1, this study does not change your reasons for taking it. It adds a mechanism story to benefits that human trials had already reported for hearts and kidneys. If you have type 1, the picture is different. No GLP-1 is approved for type 1 diabetes as of this writing; some people use one off-label with a doctor’s help, and this paper says nothing about safety, insulin needs, or DKA risk in that setting. It is a study of aging, not a study of diabetes.

The takeaway, and this is an editorial read, not the paper’s: the human evidence for these drugs that matters most was never about the scale. It was about the things that end lives early: heart attacks, kidney failure, strokes. This study offers one plausible reason those benefits show up, which is that the drug seems to push tissues toward the state that eating less produces, without the eating less. Whether that adds years is unknown. Whether it removes some of the wear along the way is the more useful question, and it is the one the human trials are built to answer. If any of this touches your care, bring it to a doctor who knows your diabetes and knows you.

Sources. The study was read in full text; it is open access. The findings above are cited to it directly:

The study. Feng Y, Barthez M, Wang Y, Chen Y, Qiu H, Wang CL, Heydari K, Delcroix M, Rasmussen LJ, Bohr VA, Chen D. Late-life semaglutide treatment slows ageing and extends lifespan in female mice. Nature, published September 2, 2026 (PubMed 42686906). Funding listed: National Institute on Aging (R01AG063404, R01AG063389, R01AG082105) and the National Institute of Food and Agriculture. No industry funding listed. Evidence tier: animal research — 20-month-old female C57BL/6 mice, 39 saline and 40 semaglutide in the lifespan arm, 10 per group in the five-month comparison.

Institutional release. UC Berkeley, Department of Metabolic Biology & Nutrition, GLP-1 treatment extends the lifespan of older, healthy mice, September 2, 2026. Used for the funding statement and author affiliations.

Outside expert comment. Science Media Centre, expert reaction, September 2, 2026. The age-62 comparison is from Dr. Laura Sinclair, University of Exeter. The exercise explanation for the brain findings is from Prof. Tara Spires-Jones, University of Edinburgh. Prof. Naveed Sattar, University of Glasgow, placed the study alongside human trial evidence on mortality; he declares consulting and speaking fees from Novo Nordisk and other manufacturers. The human outcome trials referred to above are the cardiovascular outcome studies of these drugs, for example LEADER (liraglutide in type 2 diabetes, NEJM 2016) and SELECT (semaglutide in overweight and obesity without diabetes, NEJM 2023), which measured heart attacks, strokes, and deaths, not aging.

The related beta-cell study. Van de Velde S, Yu J, Evensen KG, Pakhlevanyan E, Williams AE, Shaw RJ, Montminy M. Med14 phosphorylation shapes genomic response to GLP-1 agonists. Proceedings of the National Academy of Sciences 123(10): e2536772123, March 4, 2026. The calorie-restriction marker-gene observation in mouse islets is from this paper; the Juicebox post on it is here. The connection between the two studies is an editorial observation; neither paper cites the other.

Type 1 approval status. ClinicalTrials.gov phase 3 listings for semaglutide added to insulin in type 1 diabetes, for example NCT06894784 and NCT06082063, checked September 2026.

How to read this evidence. This is a lifespan and physiology study in one inbred strain of laboratory mouse, female only, treated with one drug at one dose starting late in life. It shows what happened to those animals. It cannot show whether semaglutide lengthens, shortens, or does nothing to a human life, and it did not study anyone with diabetes. Semaglutide (Ozempic, Wegovy) is FDA-approved for type 2 diabetes and weight management; it is not approved for type 1 diabetes.

This post is for educational purposes only and is not medical advice. Nothing here is a recommendation to start, stop, or change any medication. Talk with your doctor before making any changes to your care.

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