Weight status in young girls and the onset of puberty

OBJECTIVE. We sought to examine the association between weight status in early childhood and onset of puberty. PATIENTS AND METHODS. The study included 354 girls from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. Girls were followed longitudinally with height and weight measurements at 36 and 54 months and grades 1, 4, 5, and 6 and with assessment of pubertal stage by physical examination and maternal report in grades 4 through 6. The main outcome was the presence of early puberty, indexed as follows: (a) breast development at or more than Tanner stage 2 by physical examination at grade 4; (b) breast development at or more than Tanner stage 3 by physical examination at grade 5; (c) maternal report of breast development at or more than Tanner stage 3 at grade 5; and (d) maternal report of menarche having already occurred (yes versus no) at grade 6. Multiple logistic regression models predicting early versus late puberty were constructed by using the covariate BMI z score at 36 months, rate of change of BMI and accelerated BMI between 36 months and grade 1, race, maternal education, and maternal age of menarche. RESULTS. BMI z score at 36 months, rate of change of BMI between 36 months and grade 1, an earlier age of maternal menarche, and nonwhite race were each consistently and positively associated with an earlier onset of puberty across the various measures of puberty. CONCLUSIONS. Higher BMI z score in girls as young as 36 months of age and higher rate of change of BMI between 36 months old and grade 1, a period well before the onset of puberty, are associated with earlier puberty, which suggests that increasing rates of obesity in the United States may result in an earlier average age of onset of puberty for US girls.