New data are adding to the growing sense that GLP-1 drugs—best known for suppressing appetite and driving substantial weight loss—may be doing more than improving blood sugar and the numbers on a scale. Research presented at an aging conference in Boston suggests these medications may shift at least some markers used to estimate “biological age,” a metric intended to reflect physiological wear and tear rather than birthdays alone.
According to findings reported by the drugmakers Eli Lilly and Novo Nordisk, overweight people and individuals with diabetes who received GLP-1 therapies showed biological-age readings roughly two to three years “younger” than comparable participants given placebo. Scientists interested in aging have been floating the idea that GLP-1s could function as “longevity drugs,” though any such benefits would, at minimum, be most clearly documented so far in populations already living with obesity or diabetes.
The biological-aging results arrive amid a long list of conditions for which GLP-1 agonists are already used—or being actively explored. These drugs are approved to treat type 2 diabetes, chronic kidney disease, and obesity, and they can also be prescribed to certain people who are overweight or considered at elevated risk for specific cardiovascular problems. Beyond those indications, researchers have reported signals that GLP-1s might help with substance-use disorders, and the drugs have been investigated for potential roles in neurodegenerative disease and cancer.
Public uptake has accelerated rapidly. A recent Gallup poll found that 11% of Americans are currently taking a GLP-1 medication for weight loss, up from 3% in 2024. The survey also reported that 15% of Americans say they have used a GLP-1 drug for weight loss at some point.
With that surge has come heightened attention to safety—especially the less predictable or rarer harms that may only become apparent when millions of people use a therapy. The best-known side effects are gastrointestinal, including nausea, vomiting, diarrhea, and constipation. GLP-1 drugs have also been associated with pancreatitis and gallstone disease.
More controversial are reports of possible eye complications. Some patients have alleged that GLP-1 use triggered damage to nerves at the back of the eye. Dozens of lawsuits have been filed against Novo Nordisk and Eli Lilly by people who developed a condition that can cause sudden vision loss; plaintiffs argue the drugs contributed to their symptoms. Both companies deny the allegations, and the scientific evidence to date has been mixed.
Researchers are also probing effects on hair and nails. Savanna Vidal at the George Washington University School of Medicine and Health Sciences and colleagues analyzed electronic health records spanning 67 US health-care organizations. In that dataset, GLP-1 use was linked to a higher risk of hair loss, although the problem is not believed to be widespread. Separately, at a conference in Austria, investigators presented results from a smaller study in which 66% of GLP-1 users reported at least one nail disorder, including cases where nails detached. Nail issues were also common among people not taking GLP-1s, and the researchers did not conclude the drugs were causing nails to fall out.
Children are another major unknown. Pediatric side effects could differ from those in adults, yet data remain limited. Still, prescribing has climbed: between 2019 and 2026, GLP-1 prescriptions for US children aged eight to 11 with obesity increased 310-fold. The numbers remain small overall, but the trajectory is upward.
That context matters as global health agencies grapple with childhood obesity. This week, the World Health Organization released its first guidelines on managing obesity in children and adolescents. While estimating that 70 million children aged five to nine were living with obesity in 2024, the WHO explicitly advises against pharmacological treatment for children younger than 10, citing insufficient evidence on benefits and possible harms to growth, development, physiological function, and mental health.
Why it matters
GLP-1 drugs are reshaping obesity and diabetes care, but widespread use means even uncommon side effects can affect large numbers of people. Emerging signals—from biological-aging measures to eye, hair, and nail concerns—underscore how much remains unknown, especially for children. Watch for stronger independent studies and post-marketing safety data that clarify which risks are real, how frequent they are, and who is most vulnerable.