In 2003, U.S. Surgeon General Richard Carmona referred to the rise in obesity rates as a "pediatric health crisis." Since then, this crisis has resulted in a growing number of children experiencing high blood pressure, diabetes, sleep apnea, orthopedic problems and depression. Some studies indicate that obesity even may cause children to reach puberty at younger ages, which could lead to physical and mental health concerns later in life.
Defining Obesity
To determine if a child is overweight or obese, you need to know her body mass index (BMI). This formula assesses weight relative to height while indirectly measuring body fat. The American Academy of Pediatrics defines children and adolescents with a BMI over the 85 percentile but less than 95 percentile as overweight and those with a BMI greater than the 95 percentile as obese.
Obesity Rates
A National Health and Nutrition Examination Surveys (NHANES) study examining obesity rates in the United States from 1976 through 2006 found that the prevalence of obesity for children has increased: from 5 to 12.4 percent for ages 2 through 5 years, 6.5 to 17 percent for ages 6 to 11, and 5 to 17.6 percent for 12- to 19-year-olds.
Obesity and Early Puberty Link
Several studies suggest that the increasing rate of obesity is linked to the trend of girls reaching puberty at earlier ages. A study conducted in 1997 at the University of North Carolina-Chapel Hill first noted the declining age of puberty over the past 30 years among girls. Ten years later, a study conducted at the University of Michigan revealed that higher BMI scores in girls as young as age 3 and large increases in BMI between age 3 and first grade have been associated with earlier puberty, defined by researchers as "the presence of breast development by age nine." Few studies have found a link between BMI and puberty in boys.
Leptin and Early Puberty
Some researchers believe the ability of fat to store estrogen and trigger production of the hormone leptin is what links obesity to early puberty. In the February 2008 issue of "Pediatrics," Paul B. Kaplowitz, M.D., Ph.D., writes: "A growing body of evidence from both rodent and human studies suggests that leptin may be the critical link between body fat and earlier puberty. Leptin-deficient mice and humans fail to enter puberty unless leptin is administered. ... The linkage between body fat and the reproductive axis in girls may have evolved in mammals as a mechanism for ensuring that pregnancy will not occur unless there are adequate fat stores to sustain both the mother and the growing fetus."
Dangers of Early Puberty
Researcher Joyce Lee, M.D., MPH, who led the University of Michigan study, believes more studies examining the link between obesity and early puberty must be conducted. She points out that early puberty has been associated with earlier initiation of alcohol use and sexual intercourse as well as increased rates of behavioral problems, psychosocial stress, adult obesity and reproductive cancers. She says it is important for future studies to identify exactly how increased body fat leads to earlier puberty in girls so these effects can be prevented.
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