(BMI)
the weight of a person (in kilograms) divided by the square of the height of that person (in metres): used as an indicator of whether or not a person is over- or underweight. For example, a person who is 1.7 m tall and weighs 65 kg has a BMI of 65/1.72 = 22.5. A BMI of between 20 and 25 is considered normal, between 25 and 30 is over-weight, and greater than 30 indicates clinical obesity. A BMI of less than 20 is considered underweight.
Medical dictionary. 2011.