Novo Nordisk and Eli Lilly, the companies behind the best-selling GLP-1 weight-loss and diabetes drugs, say their medicines appear to slow molecular “aging clocks.” Scientists from both companies shared the results at the Aging Research & Drug Discovery (ARDD) meeting in Boston1, the 13th edition of the conference2. Novo’s analysis has not been peer reviewed, and Lilly’s results were presented at a conference, not in a published paper1.
Aging clocks estimate a person’s biological age from molecular signals in the body. Older versions look at changes to DNA that build up over time. Newer ones track levels of key proteins3. Both companies found that overweight or diabetic patients taking the drugs had a lower biological age than those on placebo. How large the difference was depended on which clock was used and which organ was tested3.
What Novo reported for semaglutide
Novo, which makes semaglutide (sold as Ozempic and Wegovy), took blood draws from 10,052 people: half on the drug, half on placebo3. Blood was collected at the start of the study and again months later. It was then run through “proteomic clocks,” which use protein levels to predict a person’s age and risk of dying3. The scientists analyzed existing clinical trial data rather than running a new study2.
Overall, the difference was around “two to three years,” according to Nikolaj Roed, a global project leader at Novo. He said the company has been seeing “improved biological age in our patients across trials and across different tissues”3. One clock based on heart proteins showed a slowdown of as much as four years3.
Alejandro Aguayo-Orozco, a senior scientific director at Novo, described the question the team set out to answer3:
When you intervene with semaglutide, does it actually move the clocks in any direction? And the answer is yes.
“I think it’s pretty clear that the organ age is shifting,” he said during the meeting3.
What Lilly reported for tirzepatide
Lilly scientists ran a smaller analysis of tirzepatide, which is sold as Mounjaro for diabetes and Zepbound for obesity. They used epigenetic clocks, which estimate age from accumulated changes to DNA3. Tirzepatide combines GLP-1 activity with a second gut hormone, GIP2.
Kevin Duffin, Lilly’s vice president for aging research, presented data from the SURMOUNT-5 trial. That trial randomly assigned more than 700 adults with overweight but without diabetes to tirzepatide or semaglutide for 72 weeks4. The aging analysis covered 71 participants who were on tirzepatide and over 504. Over the study period, these people would have been expected to age 1.38 years in calendar time. Across the different epigenetic clocks, the average change in biological age ran between 0.7 and 1.1 years4. Some clocks went backward, which suggests some organs and tissues measured younger than at the start4.
“All the clocks are telling a consistent story that we’re seeing a reduction in age,” Duffin said at the conference. “It’s not like we’re going to reverse age by 30 years or something, but it’s a significant reduction”3. CNN reported that Duffin put the reduction at somewhere around three to six years4.
Accounts of the comparison group differ. Gizmodo described both companies’ results as compared with placebo or a control group2. CNN reported that Duffin acknowledged there was no placebo group of people not using a weight-loss drug, and that follow-up was relatively short4. Duffin said the effects seemed to grow stronger over time and that Lilly hopes to follow people longer in its next trial4.
What the data does not show yet
None of these results show that anyone will live longer, stay sharper or avoid disease. Aging clocks are lab estimates1. The field is young, and researchers do not yet know how well improvements on these clocks track real health benefits2.
The people studied had obesity or type 2 diabetes, so it is uncertain whether people without those conditions would see any effect2. “In an unhealthy population, I do think it’s an anti-aging drug,” said Vadim Gladyshev, a Harvard biologist who helped Novo with its molecular measurements. “But in a healthy population, no one knows”3. CNN also reported that it is not yet clear whether the clock changes come from weight loss itself or from some separate effect of the drugs4.
Dr. James Kirkland, who directs the Center for Advanced Gerotherapeutics at Cedars-Sinai Medical Center, said the epigenetic and protein measures are still in development. They are useful for large groups but tell an individual little, he said, and “they can vary tremendously from day to day within a person”4. “My concern is that people could overread some of this stuff,” Kirkland said, referring to people without diabetes or obesity who are taking the drugs as a biohack4.
Several people at the meeting noted that GLP-1 drugs have side effects, including muscle loss3.
Who is behind the findings
Company scientists conducted both analyses, not independent researchers who might be more impartial2. The companies have large commercial stakes: GLP-1 drugs are the best-selling drugs in the world, with tirzepatide at the top of the list and semaglutide a close second3. More than one in 10 American adults use GLP-1 drugs for weight loss, according to the New York Post5.
Gladyshev, an academic, assisted Novo with the measurements3. The meeting’s organizer, Alex Zhavoronkov, founded Insilico Medicine. Last month he presented data suggesting one of his company’s experimental lung-disease drugs also reversed aging-clock signals3. During the event he said he has been “microdosing” the weight-loss drugs even though he is not overweight3. When he asked Aguayo-Orozco whether a reasonable person should start taking semaglutide, the Novo scientist replied: “I am not a physician. I cannot answer that question”3.
How it fits the field
Earlier studies found that GLP-1 drugs lower the risk of heart, kidney and liver disease and reduce sleep apnea and inflammation, all of which contribute to loss of health as people age4. Real-world studies have also linked them to a lower overall chance of death3. Animal studies have pointed to a possible lifespan effect too2.
Steve Horvath, a UCLA professor credited with inventing aging clocks, said: “Two years is a pretty strong effect, in my book.” He said the data could provide “evidence that these GLP-1 drugs are actually what is known as geroprotectors, medications that slow or possibly even reverse biologic aging”3.
The results also matter for the clocks themselves. Clock makers now have evidence that their readouts drop when people take drugs with broad, well-documented benefits3. “The clock people have been pushing for a decade to get this kind of study done,” said Yuge Ji, a biologist who previously worked in the field and now runs the startup Reflector Bio3.
What to watch next
- Peer-reviewed papers. Neither company’s analysis has been published in a journal yet1. Full methods, clock choices and comparison groups will matter, given the differing accounts of Lilly’s control group.
- Longer follow-up. Duffin said Lilly hopes to follow people for longer, adding that it would “be very interesting to see what happens at four or five years after treatment with a GLP-1”4.
- Healthy older adults. The US agency ARPA-H is putting $38 million toward a study of whether semaglutide affects cognition, mobility and sensory acuity in healthy people over 605. That would test the open question Gladyshev raised: what happens in people without obesity or diabetes.
