Childhood obesity is a growing global health concern, with established links to physical activity, nutrition, and, increasingly, to prenatal and perinatal factors. Emerging evidence highlights the significant role of maternal conditions such as obesity, comorbidities, nutrition, and environmental exposures in predisposing offspring to long-term metabolic and cardiovascular diseases. The "Developmental Origins of Health and Disease" (DOHaD) paradigm provides a framework for understanding how early life environmental exposures, particularly during the periconceptional, fetal, and neonatal periods, can program future health outcomes through epigenetic mechanisms. Epigenetic modifications alter gene expression without changing the DNA sequence and are increasingly recognized as key mediators in the development of obesity. This narrative review summarizes current findings on the early determinants of childhood obesity, emphasizing the molecular and epigenetic pathways involved. A comprehensive literature search was conducted across multiple databases and international sources, focusing on recent studies from the past decade. Both human and animal research were included to provide a broad perspective. This review aims to consolidate recent insights into early life influences on obesity, underscoring the need for preventive strategies starting as early as the preconception period.