Some FAQs (Frequently Asked Questions) on growth and body size of children as part of the series on Lessons in Growth & Maturation.
IS SIZE AT BIRTH RELATED TO SUBSEQUENT SIZE DURING CHILDHOOD OR ADULTHOOD?
Length at birth is not related to height during childhood or adulthood. However, birthweight, especially at the extremes – low birth weight (<2500g; <5.5 lbs) or high birthweight (>4000g; 8.8 lbs), or macrosomia (>4500g; about 10 lbs), can be related to childhood and adult obesity. Birth size, in general, is related mainly to the fetal genotype and the intrauterine environment. Stay tuned for an upcoming blog that addresses if what happens inside the womb and what the mother is exposed to and exposes the child to impacts youth sports performance.
IS HEIGHT AT AGE 5 OR 8 OR 12 YEARS OLD INDICATIVE OF ADULT HEIGHT?
Yes... with the exception of tracking during the adolescent growth spurt. The correlation between height during childhood and adolescence and adult height becomes relatively stable at about age 2-3 years with a tracking coefficient of about 0.7-0.8 (1.0 is perfect) with lower coefficient during the adolescent growth spurt, given the dynamic nature of it.
Weight is a little more variable with tracking coefficients between 0.6-0.8, and this is due to the greater influence of diet (and exercise) on energy balance and body composition.
There are several methods, including the Khamis-Roche method, that can be used to predict adult height.
ARE EARLY MATURERS TALLER AS AN ADULT?
Although early maturers are taller than average and late maturers of the same age during child/adolescence, height will be similar at age 18. This is because late maturers keep growing at a steady rate longer even though they generally experience a less intense adolescent growth spurt. But of course, genetics also plays a major role!
WHAT IS THE ROLE OF GENETICS ON HEIGHT AND BODY SIZE?
Height is one of the most heritable human traits. Most studies show that about 80% of height is due to genetics.
On the other hand, body weight and body composition are influenced more by the environment and particularly diet and exercise. The estimated heritability of body mass and %body fat is between 40-60%.