Obesity is a medical condition characterized by the accumulation of excess body fat to an extent that it may have a negative effect on health. It is typically defined using body mass index (BMI) and is evaluated in terms of its distribution (like central or abdominal obesity) and its impact on health. Obesity increases the likelihood of various diseases and conditions, particularly cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, certain types of cancer, osteoarthritis, and depression.

Causes of obesity are usually a combination of excessive food intake, lack of physical activity, and genetic susceptibility, although a few cases are caused primarily by genes, endocrine disorders, medications, or mental illness. Prevention and treatment of obesity often rely on a combination of diet changes, physical exercise, and behavioral modifications, sometimes complemented by medications or surgery.

Addressing obesity is important due to its significant impact on individual health and broader public health concerns.