Editorial concept illustrating research into ageing.
Imagine a medicine arriving late in life and still changing how much healthy time remains. That is the possibility behind a new mouse study involving semaglutide, the drug many people recognise through Ozempic and Wegovy.
In a paper published in Nature on 2 September 2026, researchers reported that treatment beginning in old age extended lifespan in female mice. It is an intriguing result with an equally important boundary: this was an animal experiment, not evidence that people can take a weight-loss medicine to live longer. Read the study.
The distinction makes the story more interesting. Scientists are asking whether a drug already associated with appetite and metabolism might help them understand why ageing bodies lose resilience.
The experiment started after the mice were already old
The researchers began treatment when the mice were 20 months old. One group received semaglutide; another received a control injection. In the survival experiment, median lifespan was 834 days with semaglutide, compared with 742 days in the control group—a difference of 92 days, or about 12% of total lifespan.
“Median” means the point by which half the animals in a group had died. It does not mean every treated mouse gained 92 days, and it provides no valid conversion into extra years for a person. The survival finding also applies to the female mice studied; it cannot automatically be extended to males. Methods and results in Nature.
Beginning late matters conceptually. A treatment that only works when started very early would answer a different question from one that changes outcomes after ageing is already well under way.
More time is only half the question
Most people would want extra years in which they could move, think and live independently. Researchers often call the period spent in good health healthspan.
In separate experiments, the team assessed physical and cognitive function as well as metabolism. UC Berkeley's account reports improvements in measures including muscle function, spatial memory and blood-sugar control. These are tests of particular abilities in mice, rather than proof that the entire ageing process has been reversed. UC Berkeley research summary.
Think of a car that still starts after many years. Its age alone tells you little about its brakes, steering or reliability. Longevity research faces a similar challenge: survival and functioning well are related, but they are not interchangeable measurements.
Was it simply eating less?
That is an obvious question for a medicine associated with appetite. The treated animals ate less, so the researchers also examined mice whose food intake was reduced by a comparable amount.
Berkeley reports that some functional and metabolic benefits differed from those produced by calorie restriction alone. That makes the comparison useful, but it does not identify a single “anti-ageing switch”. Nor should this separate experiment be confused with the lifespan comparison. Berkeley's explanation of the calorie-restriction experiments.
The next scientific job is to separate overlapping effects. A change in appetite, body composition or blood-sugar regulation might influence other parts of an animal's health. Establishing which pathways matter is harder than observing that two groups end up different.
What do we actually know in people?
Semaglutide mimics the action of a hormone called GLP-1, which helps regulate appetite and blood sugar. Its human evidence already extends beyond a number on the bathroom scales.
In March 2024, the US FDA approved Wegovy to reduce the risk of cardiovascular death, heart attack and stroke in adults with established cardiovascular disease who also had overweight or obesity. That was a specific clinical result in a defined population. It was not approval for general life extension. FDA announcement.
The medicine also has side effects and prescribing restrictions. Benefits established for one group do not establish a favourable balance for healthy people hoping to slow ageing. The new mouse paper cannot resolve that question.
What it offers is a stronger reason to investigate: a late-life intervention affected survival alongside several measures of function. Whether anything similar can be achieved safely in humans remains the question—not the conclusion.
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