Longevity Scientist Answers Your Questions About Rapamycin - Q&A

Greg Fahy's TRIM (Thymus Regeneration, Immunorestoration, and/or Mitigation) protocol is based on the idea that the dramatic drop in thymic function after puberty contributes to immunosenescence. Though the protocol includes DHEA and metformin largely for ancillary reasons, growth hormone is considered the primary active agent. Fahy's small human studies have shown increased thymic volume, reduced fat, and improvements in epigenetic aging clocks. Dr. Kaeberlein finds the data intriguing but wants to see direct measures of immune function and plans to self-experiment with pre/post MRI and immune biomarker panels.

Dr. Kaeberlein emphasizes that any discussion of protein must be paired with diet quality. He references the debate with Peter Attia about protein bars, conceding that high-quality bars can be useful but not as dietary staples. He notes that people who chronically eat very low protein often 'don't look very good and they don't seem very happy,' and that the increased cancer risk from high protein is only seen in the context of an unhealthy diet. Thus, his practical advice is to keep protein moderately high, cut out simple sugars and processed foods, and do resistance training.

He explains that these clocks typically measure DNA methylation patterns correlated with chronological age or mortality risk, not true biological age. First-generation clocks are trained on chronological age; second-generation clocks on mortality risk or pace of aging. Even the promising pace-of-aging clocks, which track changes in health over time, have not been validated in consumer-grade products. He warns that the premature rush to market could backfire when regulators see poor performance, harming credibility for responsible developers trying to use these clocks in drug approval trials.

After seeing more data on GLP-1 receptor targets outside the brain's appetite centers, he now believes there could be direct beneficial effects on age-related processes. He would like to see a lifespan study in laboratory animals. He also stresses that without resistance training and a quality diet, these drugs cause significant lean mass loss, increasing frailty, and cautions about hormonal perturbations during extreme calorie restriction.

Over the last few years, rodent studies show rapamycin boosts age-related immune function and prevents sarcopenia. Two large clinical trials of everolimus (a rapamycin derivative) in older adults showed improved vaccine response. His team's study of 333 off-label rapamycin users found lower rates of severe COVID-19 and long COVID symptoms, with no difference in infection risk. The Pearl trial from Ageless RX even hinted at improved body composition in women at very low doses. On the muscle side, he now says that if anything the needle is leaning toward better lean mass outcomes.