Obesity is classified by the World Health Organization (WHO) as a chronic, relapsing disease arising from complex interactions between genetics, neurobiology, eating behaviours, access to healthy diet, market forces, and the broader environment. In the last decades, obesity has expanded globally as countries have experienced greater food security, socioeconomic development, and shifts in diet, physical activity, and societal and individual behavior driven by globalization and industrialized food systems. These forces have created increasingly obesogenic environments, contributing to what is now a global public health crisis with more than 1 billion people living with obesity and prevalence rising in nearly every country. A diagnosis of overweight or obesity is made by measuring people's weight and height and by calculating the body mass index (BMI): weight (kg)/height? (m?). The body mass index is a surrogate marker of fatness and additional measurements, such as the waist circumference, can help the diagnosis of obesity. The BMI categories for defining obesity vary by age and gender for adults, adolescents, children and infants. In 2022, 1 in 8 people in the world were living with obesity. Worldwide adult obesity has more than doubled since 1990, and adolescent obesity has quadrupled. In 2022, 2.5 billion adults (18 years and older) were overweight. Of these, 890 million were living with obesity. In 2022, 43% of adults aged 18 years and over were overweight and 16% were living with obesity. In 2024, 35 million children under the age of 5 were overweight. Over 390 million children and adolescents aged 5-19 years were overweight in 2022, including 160 million who were living with obesity.