Weight And Puberty Onset in Girls

Question: I would like for you [Dr. Dobson] to elaborate on your statement that the timing of puberty in girls is related to fat distribution in the body. Does that mean that overweight girls always mature earlier than those who are thin?

Answer: No, but weight does seem to be involved in early and late development. For example, children who participate regularly in gymnastics and are therefore very thin are often late in developing. If you have watched women's Olympic gymnastics competitions, you must have noticed how the female participants usually have smaller breasts, have childish little voices, and are generally immature. Maturation usually occurs when they leave the sport. It is not uncommon for very thin female marathon runners to have amenorrhea, which refers to an absence of menstruation.13

Vigorous training was once believed to be very harmful to girls. When I was a boy, I remember that girls were restricted from strenuous exercise. Though it seems silly to us today, girl basketball players were not even allowed to run up and down the court. They could only play offense or defense. The rules required them to stand at the centerline waiting for the ball to be advanced to their end of the court.

How things have changed! Today, some of the best female athletes in the world, such as professional tennis players, are ranked in the top five at seventeen or eighteen years of age. Tracy Austin became the youngest player ever to win a major tournament when she claimed the U.S. Open title at the age of sixteen in 1979; Serena Williams was only a few weeks shy of her eighteenth birthday when she won the title in 1999.14 The Russian darling Maria Sharapova won the 2004 Wimbledon championship when she was just seventeen.15

As for overweight girls, it was believed until recently that obesity was causing the age of sexual maturation to decline.16 That view is now questioned. Instead, Dr. William Lassek of the University of California, Santa Barbara, says that the key factor is where the fat is located. He writes,

What our findings suggest is that menarche is likely to occur when girls have stored a certain minimal amount of fat in the hips and thighs, and that girls who tend to store more fat around the waist—who have abdominal obesity—are more likely to have delayed menarche.

Fat deposited in the hips and thighs is especially rich in omega-3 fatty acids, which are essential for the growth of the infant brain in the womb. This fat is protected from everyday use like money deposited in a bank. You are not allowed to withdraw it until late pregnancy.17

13.A. R. Glass, P. A. Deuster, S. B. Kyle, J. A. Yahiro, R. A. Vigersky, and E. B. Schoomaker, "Amenorrhea in Olympic Marathon Runners," Fertility and Sterility 48, no. 5 (November 1987): 740–745.

14.U.S. Open list of past champions; see http://www.usopen.org/en_US/about/history/wschamps .html.

15.Ladies' Singles Finals 1884–2008, Wimbledon Rolls of Honour; see http://www.wimbledon.org/en_GB/about/history/rolls/ladiesroll.html.

16.Aviva Must, Ph.D., "Back to School: Child and Adolescent Health," Pediatrics (September 2005); E. J. Mundell, "Puberty Comes Sooner for Overweight Girls," Health Day (August 11, 2005).

17.Macleod, "Her Father's Daughter."

Book: Bringing Up Girls

By Dr. James Dobson

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