Overweight Girls Most Likely to Get Heavy Before Teen Years

BALTIMORE, Jan. 8 -- The most vulnerable age for girls to initially put on too much weight is from nine to 12, and that may lead to high blood pressure and other cardiovascular risk factors, found investigators here.

According to a longitudinal study, new-onset overweight was 1.6 times more likely to occur at ages nine to 12 than later in adolescence, reported Douglas R. Thompson, Ph.D., of the Maryland Medical Research Institute, and colleagues, in the January issue of the Journal of Pediatrics.

Among 2,379 girls in the National Heart, Lung, and Blood Institute's National Growth and Health Study, overweight girls were three to 10 times more likely to have high systolic and diastolic blood pressure, low high-density lipoprotein, and elevated triglycerides and low-density lipoprotein.

"The rapid increase in overweight at age nine to 12 years suggests that this may be an especially important period on which to focus clinical and public health interventions to prevent overweight," the authors wrote.

Furthermore, the study gives an enhanced impact to the CDC's definition of overweight, said co-author Eva Obarzanek, Ph.D., of the NHLBI.

"The importance for clinicians and health care workers is that we really showed that the definition of overweight in childhood has biological significance," she said.

"Before, we just knew that if you're heavier your risk factors are higher," Dr. Obarzanek added. "Now we say they are not just higher, they meet clinical definitions of high blood pressure or high LDL."

The researchers analyzed data from 1,166 Caucasian and 1,213 African-American girls followed annually from age nine or 10 to age 18 with a further self-report at age 21 to 23 years. They were recruited from schools, health maintenance organizations and Girl Scout troops.

Overweight, defined as at or above the 95th percentile for body mass index, was present among 7.4% of Caucasian girls and 17.4% of African-American girls at age nine. By age 18, the prevalence was 10.1% and 23.3%, respectively.

New-onset overweight ranged from 2.1% to 4.8% through age 12. Thereafter, the annual incidence ranged from 0.4% to 2.2% such that the overall risk of overweight onset was 1.6 times more common at ages nine to 12 than beyond (95% confidence interval 1.1 to 2.3, P=0.03).

Because the risk of overweight onset of at any given time was 1.5 times greater for African-American adolescents than for Caucasian girls (95% CI 1.2 to 2.0, P=0.003), prevention efforts should take into account cultural differences, the investigators wrote.

The type of measurement used to define overweight had little impact on these findings. Overweight defined by percent body fat, sum of skinfolds, and waist circumference showed similar trends as the BMI-based definition of overweight.

As has been found in previous studies, overweight adolescents were 11 to 30 times more likely to be obese in young adulthood (P<0.0001).

Moreover, overweight in childhood carried substantial health risk during childhood. Overweight adolescents compared with non-overweight girls were:

• 10.0 times more likely to have a systolic blood pressure at or above the 95th percentile than non-overweight girls (95% CI 5.0 to 20.0, P<0.001).
• 3.0 times more likely to have a diastolic blood pressure at or above the 95th percentile (95% CI 1.3 to 7.3, P=0.01),
• 2.4 times more likely to have low density lipoprotein (LDL) concentrations above 130 mg/dL (95% CI 0.9 to 6.0, P=0.07).
• 6.3 times more likely to have an HDL concentration of less than 50 mg/dL (95% CI 3.4 to 11.8, P<0.001).
• 3.3 times more likely to have a triglyceride concentration of 130 mg/dL or more (95% CI 1.6 to 7.1, P=0.002).
• Not significantly more likely to have total cholesterol above 200 mg/dL (odds ratio 1.2, 95% CI 0.4 to 3.1, P=0.77).

In a secondary analysis controlling for both maturation and age, the cardiovascular risk factor estimates were generally similar though LDL levels became significantly associated with overweight (OR 3.0, 95% CI 1.3 to 7.0, P=0.01).

"Our data suggest that childhood overweight may have serious short-term and long-term consequences," they wrote.

Because the relationship between cardiovascular risk factors and overweight may already be present at age nine, they added, pediatricians should not delay in addressing the health correlates of overweight during childhood.

"Pediatricians and primary-care practitioners need to support public health and societal efforts to prevent childhood overweight by monitoring growth and providing advice to parents on the importance of their children maintaining a healthy weight during adolescence through healthy eating and regular physical activity."