BMI Prime is simple way of defining a single figure that is not immedieately related to any other units of measurement, but which can quickly and easily rank a person into a category. :Eg:
BMI Prime < 0.74 = Underweight
BMI Prime > 0.74 and < 1.00 = Optimal weight.
BMI Prime > 1 = Overweight
BMI, sometimes known as the Quetelet index, is a measure used to estimate a person's body shape based upon a person' weight and height. It originated in Belguim around the 1840's by Adolphe Quetelet. It is a simple calculation based on the individual's body weight divided by the square of their height.
BMI is particularly inaccurate for people who are very fit or athletic, as their high muscle mass can classify them in the overweight category by BMI, even though their body fat percentages frequently fall in the 10-15% category, which is below that of a more sedentary person of average build who has a normal BMI number. See wikipedia.org/wiki/Body_mass_index#Limitations for further clarification.