In a study published in the Archives of Pediatrics and Adolescent Medicine, researchers at 10 study sites across the country tracked the height and weight growth of 401 boys born in 1991, and gauged which boys had signs of genital growth indicative of puberty's onset by the time they had reached 11 1/2.
Among the roughly 28 percent of boys whose weight was consistently highest through early and middle childhood, 14 percent appeared not to have begun pubertal changes at 11 1/2 - a rate nearly twice as high as that seen among the slimmest group of boys (only 7.7 percent of whom had failed to begin puberty at that age). Among the whole group, 12.2 percent were prepubertal at 11 1/2.
The authors, led by University of Michigan pediatric endocrinologist Joyce M. Lee, said their findings offer insights into the differing processes that push girls and boys toward sexual maturation, as well as how obesity might disrupt that process in boys. They speculated that either of two hormones - the digestive hormone leptin, and the sex hormone estradiol - could play an important role in triggering boys' puberty. Both hormones in appear to be high in obese pre-adolescent boys, which might delay the onset of puberty.