Obesity is a medical condition in which excess body fat has accumulated to an extent that it may have a negative effect on health. People are generally considered 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. Obesity is correlated with various diseases and conditions, particularly cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis. High BMI is a marker of risk, but not proven to be a direct cause, for diseases caused by diet, physical activity, and environmental factors. 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.
Obesity is an important risk factor
for many chronic physical and mental illnesses. The generally accepted
view is that being overweight causes similar health problems to obesity,
but to a lesser degree.
Bariatric surgery includes a variety of procedures performed on people who are obese. Long term weight loss through standard of care procedures is largely achieved by altering gut hormone levels that are responsible for hunger and satiety, leading to a new hormonal weight set point. Bariatric surgery is a hormonal surgery in these procedures, for which the alteration in gut hormones develops as a result of the procedure's restriction and malabsorption.