CR, Fasting, and Mimetics Mapped: A Unified Longevity Intervention Framework

As global populations age, geroscience has shifted focus toward modifiable molecular mechanisms that drive biological aging. This integrative critical review, conducted by researchers at the University of Almeria, systematically analyzed 57 studies drawn from 2,132 initial records across PubMed, Scopus, and Web of Science (2004–2025), comparing caloric restriction (CR), intermittent fasting (IF), and caloric restriction mimetics on their mechanisms, clinical evidence, and translational potential.

All three intervention classes share a core molecular signature: activation of AMPK (AMP-activated protein kinase) and sirtuins (particularly SIRT1 and SIRT3), inhibition of mTOR signaling, and upregulation of autophagy. These pathways collectively regulate mitochondrial biogenesis, proteostasis, epigenetic remodeling, and inflammatory tone. CR additionally suppresses IGF-1/insulin signaling and reduces GDF-15, while IF generates ketone bodies that serve as signaling metabolites and aligns feeding windows with circadian biology. CR mimetics such as metformin activate AMPK directly, resveratrol targets SIRT1, rapamycin inhibits mTORC1, and spermidine induces autophagy via epigenetic mechanisms—each partially recapitulating CR's molecular effects without requiring strict dietary adherence.

In human clinical evidence, landmark trials like CALERIE documented that 25% CR over two years produced meaningful improvements in cardiometabolic markers and slowed epigenetic aging as measured by DunedinPACE and GrimAge clocks. IF protocols—including time-restricted eating (TRE) and alternate-day fasting—demonstrated consistent benefits on insulin sensitivity, lipid profiles, blood pressure, and hs-CRP, with circadian alignment (early TRE) appearing to amplify metabolic gains. CR mimetics showed promising signals in metabolic and inflammatory biomarkers but remain insufficiently studied in healthy aging populations, with long-term safety profiles incompletely defined.

Critically, the authors highlight pervasive methodological limitations: short trial durations, selective and predominantly non-elderly samples, reliance on intermediate rather than hard clinical endpoints (frailty, hospitalization, mortality), poor standardization of intervention definitions, and inconsistent biomarker panels. These constraints prevent definitive conclusions about longevity benefits and limit direct head-to-head comparisons across strategies.

To address translational gaps, the authors propose the AMAL (Active Management of Aging and Longevity) model—a three-level, biomarker-guided clinical framework. Level 1 involves phenotypic and metabolic profiling using standard serum markers (fasting glucose, HbA1c, HOMA-IR, TG/HDL, hs-CRP, IL-6). Level 2 incorporates aging-specific biomarkers including epigenetic clocks, circulating GDF-15, and multi-omics profiling. Level 3 applies personalized, adaptive protocols combining chrono-nutrition, exercise, and selective CR mimetics, supported by digital monitoring and AI-assisted decision tools. AMAL is presented as a working hypothesis for future clinical validation rather than a proven protocol.