Obesity is a chronic, relapsing disease characterized by excessive adiposity that threatens health on a global scale. Traditionally diagnosed using body mass index (BMI), which correlates with fat mass at a broad level, the limitations of BMI—such as its inability to account for fat distribution, muscle mass, and metabolic health—have led to recommendations for incorporating additional measurements like waist circumference. The etiology of obesity is multifactorial, caused by a complex interplay of environmental influences, genetic predisposition, and behavioral factors. Unhealthy dietary patterns, reduced physical activity, inadequate sleep, and stress interweave with factors such as socioeconomic status and rare genetic or endocrine disorders, underscoring the heterogeneity of its origins. Effective management of obesity depends on a comprehensive, evidence-based approach that prioritizes lifestyle interventions, including dietary modifications, increased physical activity, and behavioral counseling, while also considering adding pharmacotherapy and surgical options when neccesary. A “whole-of-society” strategy is essential to prevent obesity, which is one of the twenty-first century’s most pressing public health challenges.