Type 2 diabetes mellitus (T2DM) is one of the most prevalent non-communicable diseases worldwide and represents a major public health challenge because of its rapidly increasing incidence, chronic complications, and substantial economic burden. The development of T2DM is influenced by complex interactions among genetic susceptibility, aging, obesity, physical inactivity, unhealthy dietary habits, sleep disorders, psychosocial stress, tobacco use, alcohol consumption, and environmental factors. Lifestyle modification remains the cornerstone of prevention and management, with strong evidence supporting healthy nutrition, regular physical activity, weight reduction, smoking cessation, and adequate sleep. Advances in digital health, wearable devices, and artificial intelligence have further enhanced opportunities for early detection and personalized disease prevention. This review summarizes the epidemiology of T2DM, major lifestyle-associated risk factors, preventive strategies, diagnostic approaches, and future directions in diabetes prevention.