Obesity

**Definition:** Obesity is a chronic complex disease defined by excessive adiposity that can impair health. It is in most cases a multifactorial disease due to obesogenic environments, psycho-social factors and genetic variants. In a subgroup of patients, single major etiological factors can be identified (medications, diseases, immobilization, iatrogenic procedures, monogenic disease/genetic syndrome).

Body mass index (BMI) is a surrogate marker of adiposity calculated as weight (kg)/height² (m²). The BMI categories for defining obesity vary by age and gender in infants, children and adolescents. For adults, obesity is defined by a BMI greater than or equal to 30.00 kg/m² and there are three levels of severity in recognition of different management options.