Answer:
Most, if not all things that have to do with weight and stature percentiles are important when determining if that particular person has an eating disorder, or if they were just born bigger, if somebody has dwarfism, or they were just have smaller parents. The genes that person inherits are important when looking at the weight and stature of that person. i.e - it would make no sense for somebody who is a height of 6'4" to have a child who grows up and can only achieve a height of 4'0"