“Intermittent fasting slows aging”

## The Evidence A landmark 2019 review by de Cabo and Mattson in *NEJM* summarised decades of evidence: in rodents, caloric restriction (CR) consistently extends lifespan by 20–40%, and intermittent fasting (IF) extends lifespan even without CR. However, the authors note: "Results from human studies are promising but not yet definitive." Human IF trials show improvements in insulin sensitivity, inflammatory markers, blood pressure, and circulating IGF-1, but none are long enough to measure mortality directly. ## Why It Might Work IF activates autophagy (cellular self-cleaning), reduces mTOR signalling (a key aging pathway), improves mitochondrial health, and mimics the AMPK-activating effects of caloric restriction. These pathways are well-conserved across species. ## The Problem with Extrapolating From Mice Mice live 2–3 years and are highly metabolically different from humans. Many interventions that extend mouse lifespan fail in primates. The CALERIE trial (the only long-term CR trial in humans) showed metabolic improvements but no data on mortality.