Your genetics have the biggest impact on how tall you are; it determines 60%-85% of your height, in fact. What else plays a hand are the nutritional and environmental factors of your situation in life. Nutrition, in particular, has a large role: if you don’t get the nutrition you really need as you’re growing up, you won’t be as tall as you could potentially be. On the other hand, if you do get the nutrition you need, it’s most likely that you’ll hit the height that’s predetermined by your genetics. During your childhood, it’s possible that you could get just a little bit taller by a couple of inches if you eat very well and play sports.
Research has shown that getting a lot of protein during these developmental years can have a positive impact on your growth. For example, after WWII Japan had more access to fish than they had before, and as a result, the average height for the country as a whole went up by three inches. Denmark is known to have very tall people, and it’s likely due to its high wealth per capita. In general, people who are able to eat well tend to become taller–however this impact does take time, over several generations.
It’s easy to see the connection. Great nutrition can lead to an increase for height as generations go on. If you’re already an adult, this doesn’t necessarily mean that you’ll get taller if you start eating properly, however, a good, balanced diet through your developmental years could have a positive impact on your genetics. If you consume a diet of proteins, carbs, and fats, as well as a lot of fruits and vegetables, this could make a difference.
Some research has also been done with fraternal twins, to determine whether there’s a certain gene that determines our height. Fraternal twins are better for this study because their DNA is different, while their environmental factors are identical. Scientists can study how tall the twins are after they’re done developing and see if there’s a height difference. So far, this has been conducted on thousands of fraternal twins, and the options have been narrowed to chromosomes 7, 8, and 20 as the possible genes that determine our height.
Generally, once you pass puberty and are done growing, your bones will stop getting longer, and the height you’re at is the height you’ll be for the rest of your life. The reason for this are the epiphyseal plates that are located at the end of your bones. These allow bones to grow, and as you experience growth spurts, the plates expand, which causes what is known as growing pains. By the time you’re in your early twenties, your bones ossify, which means that the plates become sealed, and it’s no longer possible to add any type of growth to your bones. At that point, it’s over; it’s no longer possible to get taller.
While you’re growing up, you can eat a great, balanced diet and stretch and exercise. These things have been linked to a taller height, however, your height is mainly predetermined by your genes.