Diabetes and hypertension are pervasive, often co-existing noncommunicable diseases strongly influenced by diet, activity, and social determinants. This book presents the latest research on pathophysiology, preventive lifestyle interventions, biomarkers of early disease, and novel therapeutic strategies. It synthesizes randomized trials, observational data, and implementation studies to show which lifestyle changes produce durable benefits and how digital health tools support sustained behavior change. Sections discuss population-level policies, equity implications, and strategies for tailoring care across age groups and comorbidities. Clinicians, public-health planners, and researchers will find up-to-date evidence to inform practice and program design.