This chapter explores the historical and contemporary perspectives on fasting, encompassing its evolution from a survival mechanism to a deliberate practice for health and religious reasons. Various fasting regimens, including intermittent fasting (IF), time-restricted eating (TRE), and extended fasting (EF), are described, along with their prevalent methods and protocols. The chapter details the key metabolic and cellular mechanisms influenced by fasting, namely ketosis, autophagy, hormonal shifts, and inflammation reduction. These changes contribute to potential health benefits, such as weight loss, improved metabolic health, cardiovascular protection, enhanced cognitive function, and potentially increased longevity. However, potential risks associated with fasting, such as nutrient deficiencies and the exacerbation of eating disorders, are also discussed. The chapter concludes by emphasizing the importance of individualized approaches to fasting, guided by healthcare professionals, to maximize benefits and mitigate risks. The significance of fasting during Ramadan within a cultural and religious context is also highlighted. The chapter then introduces the subsequent chapters of the book, which explore Ramadan fasting’s impact on various aspects of health (diabetes management, cardiovascular health, liver function, immunomodulation, mental health, gene expression, gut health, maternal and fetal health, and athletic performance), its socio-environmental impact, and practical considerations for medication management and dietary modifications.