Rapamycin can add years to your life, or none at all – it’s a lottery

The longevity benefits of fasting or taking rapamycin are more like a lottery than a sure bet. The interventions were linked to a robustly extended lifespan less than a year ago, but a reanalysis of the data suggests that the benefits vary hugely between individuals.

“[They] might increase lifespan by a little bit or [they] might increase it by a lot,” says Tahlia Fulton at the University of Sydney in Australia.

The 2025 study analysed 167 research papers across eight non-human species, including fish, mice, rats and rhesus monkeys. Fulton and her colleagues found that these animals lived longer, on average, if they were given rapamycin – a potential anti-ageing drug – or were subject to a calorie-restriction regime, which has been linked to longevity. The results led the team to conclude that the same probably applied to people.

Now, the researchers have looked at the spread of the responses to the longevity interventions among the individual animals and have found that the benefits were variable. This means that at an individual level, either taking rapamycin or doing dietary restriction with the aim of living longer is “likely beneficial, but you don’t know how beneficial”, says Fulton.

“Some individuals will be much longer lived, some will be a little longer lived and some might not live any longer than they would have anyway,” she says. “You’ve got a bit of a lottery happening, and so you can’t guarantee that these treatments will increase an individual’s lifespan.”

Fulton says that the goal of a longevity intervention is to square the curve of a graph showing population size versus lifespan. This means that more people would live longer, rather than just a few, as seen with a sloping curve. “Squaring the survival curve means that everybody lives a really long, happy life, let’s say, until 100 years old, and then you pretty reliably die at 100 years old,” she says.

The latest research shows that neither dietary restriction nor rapamycin squares the curve. Off the back of this, Fulton says that expectations need to be tempered until more research is undertaken to learn who benefits from these approaches most. “Hopefully we can address individual genetic codes and life experiences and be able to say to them, ‘Alright, cool, this is exactly what you need in order to live your longest possible life.’”

Matt Kaeberlein at the University of Washington in Seattle points out that squaring the curve doesn’t necessarily improve people’s years of healthy life. He says a more interesting question is whether “healthspan inequality” increases or decreases with longevity interventions, such as exercise.

Originally developed as an immunosuppressant for people undergoing organ transplants, rapamycin blocks the action of the mTOR protein, which is key in cell growth and division. At low doses, it has been shown to increase lifespan in animals such as flies and mice, possibly by protecting against DNA damage.

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