For example, you may have genes for tallness, however, if you do not eat well and get enough rest, you may not grow properly. From birth to adulthood, body proportions change rapidly. A baby's head measures about one-fourth the length of its body. The head is only one-eighth the person's height in an adult. According to research, boys and girls grow most rapidly during the first two years of their lives.
Growth rate is much slower until the individual reaches the adolescent period.
Adolescent boys usually show this spurt of growth between the ages 12 and 17 years. This gain in height often ranges from 4 inches to 12 inches. This spurt of growth in girls usually begins two years earlier than in boys, and their growth rate is somewhat less than that of boys. Most people stop growing some time between the ages of 18 and 30. A person is usually tallest about the age of 20.