When people talk about longevity, the conversation usually comes down to one number: how long you'll live. I've never found that number very interesting on its own.
What matters to me is what those years feel like. There's a big difference between being alive at eighty and actually living at eighty - having the energy to say yes to a trip, to spend a long day on your feet without paying for it, to get up off the floor without thinking twice. Scientists even have a word for this: healthspan, the years you spend in good health, as opposed to lifespan, the years you simply get.
So when MIT Technology Review ran a piece last month titled Weight-loss drugs show signs of slowing biological aging, say drugmakers, it caught my attention right away.
What are aging clocks?
Your calendar age is how many birthdays you've had. Your biological age is how worn your body actually is. Aging clocks try to measure the second one.
They're mathematical models that read chemical tags on your DNA (epigenetic clocks) or levels of key proteins in your blood (proteomic clocks), and estimate how fast your body is aging compared with the calendar.
I think of them like a weather forecast: built on real data and genuinely useful, but still not the weather itself. A better score on a clock is a promising sign, not a guaranteed extra year of life.
What the drugmakers found
According to the MIT Technology Review piece, both companies presented new aging data at a conference:
Novo Nordisk (semaglutide). In a study of 10,052 people, about half on the drug and half on placebo, the gap between the two groups came to roughly two to three years of biological age - and up to four years on a clock that reads heart proteins.
Eli Lilly (tirzepatide). A smaller study using epigenetic clocks found that molecular time moved more slowly for most people on the drug. This is the first aging data we've seen for tirzepatide, which matters for those of us on Mounjaro or Zepbound.
Steve Horvath, the scientist credited with inventing aging clocks, called a two-year shift a pretty strong effect. But the caveats are real. These results haven't been published in a journal yet, they varied a lot depending on the clock and organ, and one leading researcher said the drugs are probably anti-aging for people who are unhealthy - but for healthy people, nobody knows.
What the published research shows
Company data is a good start, but I wanted to see what's already been checked by other scientists.
The small human study. Researchers took 84 people with HIV who carried extra belly fat and gave about half of them semaglutide for around eight months. Then they looked at their DNA. The semaglutide group was aging about 9% slower than the placebo group. The researchers think it's mostly because the drug calms down inflammation. But it's a small group, the study wasn't even set up to look at aging, and the researchers themselves say nobody's getting younger here. (Nature Communications)
The old mice. Scientists gave semaglutide to mice that were already old - think sixty-something in human years. Those mice lived about three months longer than the ones that didn't get it, roughly 12% more life (834 days vs. 742). They also stayed sharper and moved better. But they're mice. And they ate less on the drug, so it's hard to say how much of the benefit is just from eating less. (Nature)
The big one. This is the study I trust most. SELECT followed more than 17,600 people with extra weight and heart problems for over three years. On semaglutide, a little over 4 in 100 people died. On placebo, about 5 in 100. That difference sounds small, but it works out to 19% fewer deaths. It doesn't prove the drug slows aging - just that fewer high-risk people died. And in medicine, that's a big deal.
Both ways of looking at SELECT matter. "19% fewer deaths" tells you the drug is really doing something. "About 1 in 100 people" keeps it real.
Read also: Can GLP-1 Drugs Reduce Inflammation?
What I'm watching next
The study I'm most curious about hasn't finished yet. ARPA-H, a US government health agency, is putting $38 million into a Texas trial of semaglutide in healthy adults over 60. It's measuring cognition, mobility and the senses - not a score on a printout, but whether people can still think and move well as they age.
That's the question I actually care about. Results could arrive in a year or two, and I'll share them here when they do.
What this means for you right now
None of this is a reason to start a GLP-1 for aging, but if you're already on one, a few things are worth keeping in mind:
Protect your muscle. Horvath himself flagged muscle loss as a real concern. Muscle is exactly what keeps stairs, long walks and getting up off the floor easy later on. Protein at every meal and some strength training aren't optional extras. (More in Protein: 7 Key Questions Answered.)
Don't skip the small stuff. Getting myself through the gym door took weeks of debate and, in the end, a deal: ten minutes on the treadmill, then you can leave. The medication makes those small steps easier. It doesn't take them for you. (More in How to Start Going to the Gym.)
Bring it up with your doctor. If you're curious about the bigger picture - heart health, inflammation, how you're aging - it's a good conversation to have, especially now that the research is moving this fast.
Where this leaves me
I can't tell you that a weekly injection has bought me an extra decade. Nobody can yet. Lab measurements don't always turn into longer or better lives, and this science is still young.
But the direction is encouraging. Human trials, animal studies and a huge outcomes trial are all pointing the same way, and the first real test in healthy older adults is underway.
I don't just want more time. I want more good years - and the strength to use them. If GLP-1s turn out to help with that, I'll be glad. Until then, I'll keep following the research with hope, and keep showing up for the ten minutes.
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Lucas Veritas
I’m a true GLP-1 believer.
Tirzepatide (Mounjaro) user and patient advocate.
I lost 100+ lbs, found my energy and gained a new mission: helping others succeed with healthy weight loss on GLP-1s
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Disclaimer: This article reflects my personal experience and independent research. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before making decisions about your health or treatment plan.
Scientific References for this article:
Weight-loss drugs show signs of slowing biological aging, say drugmakers (Antonio Regalado, MIT Technology Review) - October 2026
https://www.technologyreview.com/2026/10/06/1145836/weight-loss-drugs-glp1-lilly-novo-aging-clocks/Semaglutide slows epigenetic aging in a randomized trial of HIV-associated lipohypertrophy (Corley MJ, Dwaraka VB, Pang AP, et al. Nature Communications) - 2026
https://doi.org/10.1038/s41467-026-72861-3Late-life semaglutide treatment slows ageing and extends lifespan in female mice (Feng Y, Barthez M, Wang Y, et al. Nature) - September 2026
https://doi.org/10.1038/s41586-026-10940-7The Effect of Semaglutide on Mortality and COVID-19-Related Deaths: An Analysis From the SELECT Trial (Scirica BM, Lincoff AM, Lingvay I, et al. Journal of the American College of Cardiology) - 2024
https://www.jacc.org/doi/10.1016/j.jacc.2024.08.007
