Obesity is a medical condition in which excess body fat has accumulated to the 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, is over kg/m2, with the range 30 kg/m2 defined as 25–30overweight. Some East Asian countries use lower values. Obesity increases the likelihood of various diseases, particularly heart disease, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis.
Obesity is most commonly caused by a combination of excessive food intake, lack of physical activity, and genetic susceptibility. A few cases are caused primarily by genes, endocrine disorders, medications, or mental illness. Evidence to support the view that obese people eat little yet gain weight due to a slow metabolism is not generally supported. On average, obese people have a greater energy expenditure than their thin counterparts due to the energy required to maintain an increased body mass.
Obesity is a monthly peer-reviewed medical journal covering research into obesity. It was established in 1993 under the name Obesity Research, obtaining its current name in 2006. It is published by Wiley-Blackwell on behalf of the Obesity Society, of which it is the official journal. The editor-in-chief is Eric Ravussin (Pennington Biomedical Research Center). According to the Journal Citation Reports, the journal has a 2013 impact factor of 4.389.