Weight-loss drugs show signs of slowing biological aging, say drugmakers

Popular weight-loss drugs, such as Ozempic and Wegovy (both based on semaglutide) from Novo Nordisk, and Mounjaro and Zepbound (both based on tirzepatide) from Eli Lilly, are primarily designed to help people lose weight by acting on a receptor called GLP-1 in the brain, which reduces hunger. These drugs have become the best-selling medications worldwide, with tirzepatide generating over $36 billion in revenue for Lilly in 2025 alone. Semaglutide, sold under multiple names, was the second-highest revenue-generating molecule. Beyond weight loss, these drugs have shown additional health benefits, including improved kidney function, reduced blood pressure, and a significant decrease in overall mortality risk.

Aging clocks are scientific tools that measure a person’s biological age—how old their body feels—rather than their chronological age, which is simply the number of years since birth. These clocks analyze changes in DNA or levels of specific proteins in the blood. Older methods focused on DNA changes, while newer proteomic clocks track protein levels to predict age and even risk of death. For example, one proteomic clock can estimate a person’s age by examining proteins in their blood. These clocks are not yet fully proven as reliable biomarkers, but they provide insights into how interventions like drugs might affect aging.

Recent studies by Novo Nordisk and Eli Lilly found that patients taking their GLP-1 drugs showed a reduction in biological age compared to those taking a placebo. The reduction varied depending on the type of aging clock used and the organ tested, but the overall difference was about two to three years. In one case, a proteomic clock measuring heart proteins showed a slowdown of up to four years. Scientists like Nikolaj Roed from Novo Nordisk reported improved biological age across trials and tissues. These findings suggest that GLP-1 drugs may act on fundamental causes of aging, potentially making them geroprotectors—medications that slow or even reverse biological aging.

The emerging data on GLP-1 drugs and aging clocks has been a significant validation for the science of aging clocks. Researchers have long sought evidence that these clocks can reflect real changes in aging when people take beneficial drugs. Yuge Ji, a former biologist in the field, described the findings as "huge" for the clock-making community. Novo Nordisk’s study involved blood samples from 10,052 people, half on the drug and half on a placebo, analyzed using proteomic clocks. Eli Lilly’s smaller study used epigenetic clocks, which measure DNA changes, and also found a consistent reduction in biological age for those on the drug.

Experts like Steve Horvath, who invented aging clocks, and Vadim Gladyshev, a Harvard biologist, suggest that GLP-1 drugs could be among the first mass-market anti-aging remedies. However, Horvath notes that the evidence is strongest for unhealthy populations, such as those with obesity or diabetes, and it remains unclear whether healthy individuals would benefit similarly. The drugs do have side effects, including muscle loss, which may limit their use for some people. Horvath stated that he hasn’t seen sufficient evidence to recommend them for non-obese individuals yet. The question of whether these drugs can benefit healthy people is still under investigation.