For how we live.
The only long randomised trial of calorie restriction in non-obese adults improved cardiometabolic risk and modestly slowed one measure of biological ageing. Participants never hit the 25% target.
The dream was 'compression of morbidity' — sickness squeezed into a short window before death. Across 183 countries the healthspan–lifespan gap instead grew to 9.6 years, and to 12.4 in the US.
Five-day fasting cycles improve risk markers and one 'biological age' estimate in small trials. No human study has yet shown the diet prevents disease or extends life.
No pill in the anti-ageing market has mortality data like physical activity. The largest cohorts show most of the benefit arrives at half the recommended dose, and more brings diminishing returns.
Very long life carries real genetic signals — the APOE gene most robustly, FOXO3 in some populations. But pedigree studies put the true heritability of human lifespan well below 10%.
Two large cohorts link purpose in life to lower mortality and lower Alzheimer's risk. Whether purpose protects health, or health sustains purpose, is what the studies cannot fully separate.