Nature published a mouse study last Wednesday. If you keep up with longevity news, you’ve probably already seen the headline.
What?
On September 2, a team at Berkeley reported that semaglutide, the drug in Ozempic and Wegovy, increased the median lifespan of older female mice. Their median lifespan rose from 742 days to 834 days, a gain of 92 days, or about 12%. The treatment began when the mice were 20 months old, which is similar to a woman in her sixties. These mice were healthy, not obese.
The drug reduced the mice’s food intake by 24%. To compare, the team put 10 mice on the drug and 10 others on a diet with the same 24% reduction, then followed both groups for five months. The mice given the drug did better in three areas: exploratory drive, spatial memory, and blood sugar control. This research was publicly funded, and the University of California has applied for a patent to use these drugs for healthy aging.
So what?
Calorie restriction has increased lifespan in many lab animal studies. But keeping up a 24% reduction is tough for people: those in the CALERIE study, assigned to 25% restriction, managed about 12% over two years. In mice, semaglutide matched the food reduction and led to better results in three functional areas. However, they tested its survival benefit only against untreated controls.
This is the first longevity result in a while that I find truly interesting. The key comparison (drug versus diet for survival) is still ongoing, and they haven’t reported results yet. Nir Barzilai, a longevity researcher at the Albert Einstein College of Medicine who wasn’t involved in the study, put it well: “Maybe calorie restriction increases the lifespan more? The data is not there, and it bugs me.” When asked why the drug outperformed the diet on those three measures, Danica Chen, who led the study, replied, “The short answer is: we don’t know yet.”
The study only used female mice of one strain, all living in cages. While it measured muscle function, it didn’t address a question I often see in practice: what happens when people combine the drug with progressive resistance training and enough protein.
Now what?
If you’re already taking semaglutide for a medical reason, this mouse study doesn’t give you any reason to change or stop your treatment. Keep progressive resistance training in your routine and talk to your doctor about making sure you get enough protein.
If you’re thinking about using semaglutide to slow aging, keep in mind that no randomized trial has tested it for human aging or used lifespan or healthspan as the main goal. The SELECT trial found fewer deaths in people at high risk for heart problems, but it wasn’t a longevity study.
The main evidence for humans is in cardiovascular risk, so that’s what you should discuss with your doctor. In the trial, 17,604 adults with heart disease, a BMI of 27 or higher, and no diabetes saw major heart events drop from 8.0% to 6.5% over about three years. Novo Nordisk, the company that sells the drug, funded the study.
The next time you see a claim that something “extends lifespan,” check which species, the sex, and the age at first dose before looking at the percentage. It only takes a few seconds and helps you make sense of most claims.
I’ll share more on this topic when the results from the ongoing survival comparison are available.
Stay healthy.
Andre