Body mass index and waist-to-height changes during teen years in girls are influenced by childhood body mass index.
OBJECTIVE
This study examined longitudinal changes in waist-to-height ratio and components of body mass index (BMI) among young and adolescent girls of black and white race/ethnicity.


METHODS
Girls were recruited at age 9 years through the National Heart, Lung, and Blood Institute Growth and Health Study (NGHS) and were followed annually over 10 years. Girls were grouped into low (<20(th) percentile), middle, and high (>80(th) percentile) BMI on the basis of race-specific BMI percentile rankings at age 9, and low, middle, and high waist-to-height ratio, on the basis of waist-to-height ratio at age 11. BMI was partitioned into fat mass index (FM) and fat-free mass index (FMI).


RESULTS
Girls accrued fat mass at a greater rate than fat-free mass, and the ratio of fat mass to fat-free mass increased from ages 9 through 18. There was a significant increase in this ratio after age at peak height velocity. Participants with elevated BMI and waist-to-height ratios at age 18 tended to have been elevated at ages 9 and 11, respectively. There were strong correlations between BMI at age 9 with several outcomes at age 18: BMI (.76) and FMI (.72), weaker but significant with FFMI (.37), and ratio of fat mass to fat-free mass (.53). In addition, there was significant tracking of elevated BMI from ages 9 through 18.


CONCLUSIONS
In girls, higher BMI levels during childhood lead to greater waist-to-height ratios and greater than expected changes in BMI by age 18, with disproportionate increases in fat mass. These changes are especially evident in adolescent girls of black race/ethnicity and after the pubertal growth spurt.
Biro
Frank M
FM
Division of Adolescent Medicine, Cincinnati Children's Hospital Medical Center, Adolescent Medicine (ML-4000), Cincinnati, Ohio 45229, USA. frank.biro@cchmc.org
Huang
Bin
B
Morrison
John A
JA
Horn
Paul S
PS
Daniels
Steven R
SR
D000293:Adolescent; D001741:Black or African American; D001827:Body Height / Q000208:ethnology; D015992:Body Mass Index; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D009765:Obesity; D011627:Puberty; D014481:United States; D055105:Waist Circumference / Q000208:ethnology; D044465:White People