Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, such as increasing the likelihood of heart disease, diabetes, obstructive sleep apnea, and osteoarthritis. Obesity is most commonly caused by a combination of excessive food energy intake, lack of physical activity, and genetic susceptibility. It is one of the most serious health problems of the 21st century, especially in those highly developed countries, with increasing prevalence in adults and children.