Obesity is a condition where natural energy reserve, stored in the fatty tissue of humans and mammals is increased to a point where it is thought to be a significant risk factor for certain health conditions as well as increased mortality. Obesity in wild animals is relatively rare, but it is common in domestic animals like pigs and household pets who may be overfed and underexercised.
Excessive body weight has been shown to correlate with various important diseases, particularly cardiovascular disease, diabetes, sleep apnea and osteoarthritis. It is also considered a risk factor for certain cancers. Interventions, such as diet and exercise as well as medication and weight-loss surgery in severe cases are frequently recommended to reduce the risk of developing disease.
Obesity is a concept that is being continually redefined. In humans, the most common statistical estimate of excess fat mass is the body mass index (BMI), calculated by dividing the weight by the height squared; its unit is therefore kg/m2, although no actual surface is implied. The BMI was created in the 19th century by the Belgian statistician Adolphe Quetelet.