a medical condition in which accumulated excess body fat may have a negative effect on health; Â obesity is often defined by a person’s BMI (body mass index)an index used to indicate whether a person is over- or underweight. It is obtained by dividing a person's weight in kilograms by the square of their height in meters. An index of 20-25 is normal (medical definition); BMI over 25, and 20 pounds overweight, serious obesity is 100 pounds overweight
