In recent times, there has been growing interest in understanding the factors contributing to prolonged and healthy lifespans observed in specific populations, tribes, or countries. Factors such as environmental and dietary play significant roles in shaping the ageing process and are often the focus of inquiries seeking to unravel the secrets behind longevity. Among these factors, diet emerges as a primary determinant, capable of either promoting or mitigating the onset of age-related diseases that impact the ageing trajectory. This review examines the impact of various diet types on ageing and age-related conditions, including cardiovascular disease, cancer, neurodegenerative disorders, and metabolic syndrome. Different dietary patterns, such as the Mediterranean diet, the Japanese diet, vegetarian and vegan diets, as well as low-carbohydrate and ketogenic diets, are evaluated for their potential effects on longevity and health span. Each diet type is characterized by distinct nutritional profiles, emphasizing specific food groups, macronutrient compositions, and bioactive components, which may exert diverse effects on ageing processes and disease risk. Additionally, dietary factors such as calorie restriction, intermittent fasting, and dietary supplementation are explored for their potential anti-ageing and disease-modifying effects. Understanding the influence of various diet types on ageing and age-related diseases can inform personalized dietary recommendations and lifestyle interventions aimed at promoting healthy aging and mitigating age-associated morbidities.