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—is over 30 kg/m2; the range 25–30 kg/m2 is defined as overweight. [Source: Wikipedia ]