Fig. 4.

BMI varies considerably during puberty among lean but not heavy girls. Shown is the median BMI-percentile for heavier (≥71%ile BMI, dashed line) and leaner girls (<71%-ile BMI, dotted line) at the B2-visit-age (integer years). The median ages-at-B2 differed by 12 months between heavier and leaner girls in this sample, estimated from Kaplan-Meier analyses. Thus the vertical lines at 8.7 and 9.7 years are when half of the girls had reached B2 by that age. The slight upswing in median BMI% for leaner girls from 11–13 years of age is similar to the rising pattern of estrogen levels found among leaner girls by Biro et al., 2014, suggesting a reciprocal relationship between BMI and estradiol among lean girls with later age-at-B2.