Calorie Restriction

Research summary

• Caloric restriction (CR) is one of the most robust life-extension interventions in animal biology, but direct human lifespan evidence does not exist and probably never will via RCT.
• In rhesus monkeys, results have been genuinely mixed between the field's two flagship studies: the University of Wisconsin cohort found moderate CR delayed aging-related death, with 80% of CR animals surviving versus 50% of controls at the reported time point, and delayed diabetes, cancer, cardiovascular disease and brain atrophy, while the parallel NIA study found no significant survival benefit from CR.
• A later joint reanalysis by both research groups attributed much of the discrepancy to differences in diet composition and the age CR began, and concluded that CR's health benefits — though not consistently its survival benefit — are conserved across the two studies.
• In humans, the CALERIE trials are the only rigorous, sustained RCTs: 218 non-obese adults randomized to roughly 12% sustained calorie restriction for two years showed improved cardiometabolic risk factors (LDL, blood pressure, insulin sensitivity), reduced inflammatory markers, and a measurable slowing of one epigenetic pace-of-aging clock (DunedinPACE), without harming mood, cognition or quality of life.
• However, CALERIE only ran two years and measured biomarkers and surrogate aging clocks, not actual lifespan or disease incidence — the trial's own investigators state that a conclusive test of the geroscience hypothesis in humans requires much longer follow-up.
• The gap between strong mechanistic/animal plausibility and thin, short-duration human outcome data is the central honesty point for this topic.