The lifespan benefits derived from fasting and rapamycin usage resemble a lottery rather than a guaranteed outcome. While significant lifespan increases have been observed within a year, reanalysis indicates that results can vary significantly among individuals.

Talia Fulton, a researcher at the University of Sydney, mentions, “[They] may enhance your lifespan marginally [they] could dramatically increase it.”

The 2025 study examined 167 research papers across eight non-human species, including fish, mice, rats, and rhesus macaques. Fulton and her team discovered that when these animals were treated with rapamycin, a promising anti-aging compound, alongside calorie restriction — known for fostering longevity — they exhibited a longer lifespan on average. This suggests the same potential could extend to humans.

Current research has investigated the varied responses to longevity interventions in individual animals, revealing significant variability in benefits. Fulton notes that while taking rapamycin or implementing dietary restrictions appears “likely to be advantageous, the degree remains uncertain.”

According to her, “Some may experience considerable lifespan extension, while others may see minimal impact, or not outlive their expected lifespan.” This variability creates a somewhat unpredictable environment, meaning these treatments cannot guarantee lifespan extension for all individuals.

Fulton emphasizes that the objective of longevity interventions is to balance the population size with life expectancy through a squared curve. This implies that more individuals could lead longer lives, contrasting with the current trend of fewer individuals achieving longevity. “Squaring the survival curve means a larger number will lead extended and fulfilling lives until around 100, at which point mortality becomes almost certain,” she elaborates.

Current findings indicate that dietary restrictions and rapamycin do not effectively square this longevity curve. In this context, Fulton advises holding off on high expectations until further research clarifies who stands to benefit most from these approaches. “We aspire to decode individual genetic variables and life histories, ultimately determining ‘This is precisely what you need to achieve maximum longevity,'” she states.

Researchers like Matt Kaeberlein from the University of Washington stress that squaring the curve does not inherently mean enhanced health profiles. A more compelling consideration, he argues, is whether longevity initiatives, such as exercise, influence “healthspan inequality.”

Originally developed as an immunosuppressant for organ transplant patients, rapamycin inhibits the mTOR protein, essential for cell growth and division. At lower doses, it has demonstrated the potential to extend lifespan in species like flies and mice, potentially by safeguarding against DNA damage.