US scientists have shown that being overweight as a toddler increases the chance that a girl will reach puberty early.
The study from the University of Michigan’s Mott Children’s Hospital is published in the journal Pediatrics.
Dr Joyce Lee, the lead author, and colleagues used the data on 354 girls from age 3 who were enrolled in the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development (SECCYD).
SECCYD is a national programme run by the National Institutes of Health (NIH) where qualified researchers are permitted access to datasets if they fulfill the NICHD criteria.
The SECCYD data set offered the researchers the opportunity to look at longitudinal data on the girls at age 3 and 4.5, and then at school grades 1, 4, 5 and 6.
They looked at height and weight at each measurement stage, and from grades 4 to 6 they also looked at pubertal stage measurements (these were based on physical examination reports and reports completed by the girls’ mothers). They also took into account other factors such as race, the mother’s education and the mother’s age when she started menstruating.
The girls’ pubertal stage was assessed according to stage of breast development and start of the menstrual cycle.
Breast development was measured using Tanner Stages, a way of assessing physical development in children. For girls’ breasts Tanner Stage 1 is prepubertal and has no glandular tissue and Stage 2 is where the breast buds are forming. There are five Tanner stages altogether, with fully formed adult breasts at Stage 5.
Dr Lee and her team used statistical logistic regression to predict early versus late puberty from Body Mass Index (BMI) which combines weight and height.
Of the 354 girls, 168 of them (48 per cent) were classed as being “in puberty” by the age of 9, with 6.5 per cent having started their menstrual cycle by age 11.
The results showed that an earlier onset of puberty was positively and consistently linked to rate of change of BMI between age 3 and grade 1, an earlier age of the mother’s own start of menstruation, and being non-white.
The researchers said that before this study, all we knew was that higher BMI was linked to earlier onset of puberty but not which caused the other. Now this study shows it is highly likely that high BMI causes early puberty.
Other studies have shown that children are more obese than they were 30 years ago, and also that puberty in girls starts earlier than 30 years ago. Dr Lee and colleagues said their study offers strong evidence that being overweight in pre-puberty is what causes the early onset of puberty in girls.
Early onset of puberty in girls is a serious health issue because it is linked to increased mental problems, early abuse of alcohol, early sexual encounters and teenage pregnancy. It is also linked to increased obesity as a grown up and reproductive cancers, said the researchers.
“Weight Status in Young Girls and the Onset of Puberty.”
Joyce M. Lee, Danielle Appugliese, Niko Kaciroti, Robert F. Corwyn, Robert H. Bradley, and Julie C. Lumeng
Pediatrics Vol. 119 No. 3 March 2007, pp. E624-E630
doi:10.1542/peds.2006-2188 Medical News Today