mTOR (mechanistic target of rapamycin) is a serine/threonine kinase that integrates nutrient, growth factor, and stress signals. The cellular decision-maker between growth and conservation.
Mechanism — Two complexes: mTORC1 (sensitive to amino acids, especially leucine; rapamycin-sensitive) drives protein synthesis, lipogenesis, ribosome biogenesis. mTORC2 regulates cytoskeleton and survival. Chronic mTORC1 activation accelerates aging; cyclic suppression (fasting, rapamycin) extends lifespan.
Use case — Cycle mTOR activation. Train and eat protein for growth phases; fast and use plant-dominant intervals for maintenance and longevity phases. Rapamycin pulses are the pharmacologic lever.
Caveats — Chronic mTOR suppression is catabolic — you lose muscle. The successful longevity protocols pulse mTOR — they don't crush it.