

Some of the known causes are diet, physical activity, automation, urbanization, genetic susceptibility, medications, mental disorders, economic policies, endocrine disorders, and exposure to endocrine-disrupting chemicals. Obesity has individual, socioeconomic, and environmental causes.

A reciprocal link has been found between obesity and depression, with obesity increasing the risk of clinical depression, and also depression leading to a higher chance of developing obesity. High BMI is a marker of risk for, but not a direct cause of, diseases caused by diet and physical activity.

Obesity is a major cause of disability and is correlated with various diseases and conditions, particularly cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis. Some East Asian countries use lower values to calculate obesity. People are classified as obese when their body mass index (BMI)-a measurement obtained by dividing a person's weight by the square of the person's height (despite known allometric inaccuracies )-is over 30 kg/ m 2 the range 25–30 kg/ m 2 is defined as overweight. Obesity is a condition in which excess body fat has accumulated to such an extent that it may have a negative effect on health.
