This collation returns the WHO Classification for BMI. It takes the result of the BMI collation (a numerical value or a NULL) and categorizes it into the WHO classifications:
Underweight - BMI [10, 18.5)
Normal Weight - BMI [18.5, 25)
Pre-obese - BMI [25, 30)
Obese class 1 - BMI [30, 35)
Obese class 2 - BMI [35, 40)
Obese class 3 - BMI [40, 80]