Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have a negative effect on health, leading to reduced life expectancy and/or increased health problems. In Western countries, people are 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, exceeds 7002294199500000000♠30 kg/m2, with the range 25-7002294199500000000♠30 kg/m2 defined as overweight.