Earlier this month, Biohack reported that Novo Nordisk and Eli Lilly say people on their drugs aged more slowly on lab-based aging tests, in company analyses that were not peer reviewed. This article adds a different kind of evidence on the same question: a controlled animal study, reviewed by outside scientists and published in the journal Nature, that measured how long the animals actually lived.
Researchers led by UC Berkeley found that semaglutide, the drug sold as Ozempic and Wegovy, extended the lifespan of older, healthy female mice1. Mice that started the drug late in life had a median lifespan of 834 days, compared with 742 days for untreated mice, an increase of about 12%2.
What the researchers did
The team gave semaglutide to female mice that were 20 months old, roughly equal to women in their 60s2. The mice got daily injections for the rest of their lives, while a comparison group got salt-water (saline) shots instead3. The study was published in Nature on September 23. The lead author was Yufan Feng, a postdoctoral researcher in the lab of Danica Chen, a professor of metabolic biology and nutrition at Berkeley1.
Semaglutide belongs to a family of drugs called GLP-1 drugs. They copy a natural hormone that makes people feel full and helps control blood sugar3. Chen has studied calorie restriction, meaning eating much less, for two decades. Because the drug also makes people eat less, she wondered if it could act as a stand-in for dieting2.
Berkeley’s announcement described the gain as about 100 days on average1, and a summary of the NIH release called it a median of nearly 100 days4. The exact figures reported by independent coverage were 742 and 834 days25.
The evidence so far
After three months on the drug, treated mice did better than untreated mice on muscle and thinking tasks1. They explored more, balanced longer on a rotating rod, ran farther on a treadmill and solved a maze faster. Those gains held even after the researchers accounted for the treated mice being leaner2.
The researchers also looked inside the animals’ tissues. Gene activity showed less inflammation and less decline in the body’s ability to repair itself1. Coverage of the paper also listed reduced DNA damage3 and changes in cell aging, the cell’s energy centers and stem cells5.
The drug versus a diet
Because semaglutide cuts appetite, the key question was whether the mice simply benefited from eating less. In a separate five-month test, one group of 20-month-old female mice got the drug and another was fed 24% less, an amount designed to match what the treated mice ate4.
The two groups ended up with similar body weight and fat loss and performed alike on endurance and coordination tests3. Scientific American reported the drug matched the diet on muscle strength and coordination2. Where they differed, the drug group came out ahead on memory, exploration and blood-sugar control32. Metabolic rate, how fast the body burns energy, slowed in the dieting mice but stayed largely unchanged in the drug-treated mice1.
When the team compared liver gene activity with existing data on dieting, the overlap was large: both quieted inflammation and fat processing2.
“These differences point to the possibility that GLP-1 drugs tap into a biological pathway independent of calorie restriction,” said Chen.
What it does not show yet
The study does not show that Ozempic or similar drugs extend human life4. Berkeley’s own announcement said there is no indication similar results could be achieved right away in humans1.
Only female mice were used. The researchers left out males because they are more aggressive, which could complicate the results3. “One intervention that works in one gender does not necessarily generalize to another gender,” Ho Ko, a neuroscientist at the Chinese University of Hong Kong, told Nature3.
The study also does not say whether the drug or the diet adds more years of life. “The data is not there, and it bugs me,” said Nir Barzilai of the Albert Einstein College of Medicine, who was not involved2. Chen said that experiment is under way2. Why the drug beats dieting on some measures is unclear. “The short answer is: we don’t know yet,” Chen said2.
Some outside scientists raised safety points. Matt Mendoza of the University of Texas Medical Branch warned that muscle loss, which often comes with weight loss, is a particular worry in older adults and could speed up frailty3. Richard DiMarchi of Indiana University said the finding “aligns with expectations” but that “it is best to temper our enthusiasm,” adding that mice are inbred and that safety is essential for use in healthy people6.
Who is behind it
The study was funded by the US National Institute on Aging and the National Institute of Food and Agriculture. Co-authors included researchers from the University of Copenhagen and the National Institute on Aging1. Rafael de Cabo, a senior investigator at the National Institute on Aging, wrote a commentary on the study4. The sources do not show any drugmaker funding for the work.
Among the outside voices, Randy Seeley of the University of Michigan, who has previously consulted for Novo Nordisk and Eli Lilly, told Newsweek that trial data show these drugs reduce deaths from all causes in the patients studied6. Michael Corley of UC San Diego, who was not involved, called it “a very rigorous animal study that showed a positive signal”3.
How it fits the field
Scientists have known for decades that eating much less can slow aging in animals, but strict diets are hard to keep up3. A drug that offers some of the same effects without constant hunger has long been a goal2.
Evidence in people is thinner and mixed. Matt Kaeberlein, a biogerontologist, told National Geographic the mouse findings are impressive but do not yet prove the drugs slow aging, and that evidence in people will be much more speculative for now5. Raghav Sehgal of Yale School of Medicine said that in his analysis of 51 longevity approaches, semaglutide did not lower biological age in the healthy older adults included5. That contrasts with the drugmakers’ unreviewed aging-clock data covered in our earlier article, which involved people with obesity or diabetes.
What to watch next
- Diet versus drug lifespan results. Chen’s team is running the experiment that compares how long dieting and drug-treated mice live2.
- Male mice. Outside scientists said more mouse testing is needed, especially because only females were studied3.
- Studies in healthy older people. Chen said future clinical studies may test these drugs in healthy older adults4.
