This volume explores the groundbreaking disciplines of epigenetics and psychoneuroendocrineimmunology (PNEI)-two rapidly evolving fields that reveal how everyday choices profoundly influence our biological and psychological well-being.Through a carefully structured, evidence-based approach, each chapter illuminates how nutrition and physical activity extend far beyond aesthetics, shaping DNA expression, immune function, endocrine balance, and psychosocial dynamics. These lifestyle factors help delineate the line between health and disease, offering a powerful framework for preventive and personalized medicine. Written in a clear and accessible style, the text bridges the gap between cutting-edge science and practical application, making it an essential resource for healthcare professionals (including psychologists, nutritionists, and physicians), exercise scientists, fitness practitioners, and all readers passionate about integrative health. Readers will discover how lifestyle interventions can modulate gene expression-with effects potentially transmitted to future generations.