2. Pubertal Growth and Development

Breast development

True breast development in both females (thelarche) and males (gynecomastia) is due to growth of glandular tissue, not fat. For adolescents who appear to be developing breast tissue, it is important to differentiate between glandular tissue (firmer and somewhat tender tissue immediately under the areola) and fat (increase in fat in the breast tissue, along with fat in other sites of the body). Some overweight adolescents may not be developing sexually, but merely increasing the amount of fat in their breast tissue. If a pre-pubertal girl or boy is already overweight, she/he can be expected to gain weight even more rapidly when she/he eventually does go through puberty.


Weight

Between 8 and 14 years of age, girls tend to gain weight more rapidly than boys, but the 50th percentile BMI-for-age measures for girls and boys are nearly identical. A girl at the 50th percentile gains four times as much weight between 10 and 14 years of age as she does between 16 and 20 years of age (40 pounds, compared to 10 pounds). After 14 years of age, weight continues to increase, but at a decreased rate. Because boys have their growth spurt about two years later than girls, the maximum rate of weight gain for boys is between 12 and 16 years of age. A boy at the 50th percentile in weight-for-age gains about 45 pounds over those four years, while he gains an additional 20 pounds between 16 and 20 years of age.


Stature

Until 10 years of age, boys and girls grow in stature at nearly identical rates. Around 10 years of age, girls at the 50th percentile begin to grow taller more rapidly than boys. The growth rate for girls continues to be greater than boys between 10 and 13 years of age. After 13 years of age, the height spurt of girls generally is completed and the boys' height spurt is in its early phase. Therefore, by 14 years of age boys are taller than girls, on average. Girls generally gain no more than 2 inches in stature after the onset of menstrual periods. However, males can continue to grow in stature in their early twenties. By the time that adult stature is reached, the 50th percentile for stature-for-age is about 6 inches higher for males than for females. Thus, the average adult male is about 70 inches tall, and the average adult female is about 64 inches tall.