Chart your BMI against the national average

## Knowing your BMI may save your life

*These risks are associated with overweight and obese adults*

Adults whose BMI is larger than 25 (

*overweight*) or whose BMI is over than 30 (

*obese*) have an elevated risk for many diseases and health conditions, including,:

## Derivation

Body Mass Index Prime is method of using the results of the BMI calculations to 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

The BMI, also 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.

## The maths

Behind BMI

- BMI = weight(kilograms) / height
^{2} (metres^{2}) (Metric Units)
- BMI = 703 . weight(pounds) / height
^{2} (inches^{2}) (Imperial Units)

## BMI limitations

BMI is proportional to the mass and inversely proportional to the square of the height. So, if all body dimensions double, and mass scales naturally with the cube of the height, then BMI doubles instead of remaining the same. This results in taller people having a reported BMI that is uncharacteristically high, compared to their actual body fat levels.

*See wikipedia.org/wiki/Body_mass_index#Limitationsinfomation*.