Obesity can trigger puberty earlier in girls and researchers from the University of Michigan Health System (UM) now believe the opposite may be true in boys, where the extra weight contributes to a later onset of puberty.
Published in the Archives of Pediatrics and Adolescent Medicine, the study is the first to document that a higher body mass index (BMI) during early and mid-childhood for boys is associated with later onset of puberty. "[It's] the opposite of what we have seen in girls, as heavier girls tend to develop earlier, rather than later. Our study shows that the relationship between body fat and timing of puberty is not the same in boys as it is in girls," says UM's Joyce M. Lee, the study's lead author.
She adds that with childhood obesity rates more than doubling in the U.S. during the past two decades, it has become increasingly important to better understand the ways in which excess body fat can impact children's growth and development. "Although there have been a number of studies looking at the link between body fat and puberty in girls, few studies have been performed in boys. Our findings have important implications for understanding sex differences in physiological mechanisms of puberty," explained Lee.
In the study, the boys were divided into low, intermediate, and high BMI groups. Puberty was measured by Tanner genitalia staging. This defines "later onset of puberty" as a lack of genital development by 11.5 years of age. Boys in the low group were on the thinner side throughout childhood, while children in the high group were on the heavier side. Of boys in the low BMI group, 7 percent had later onset of puberty. Of boys in the intermediate BMI group, 13 percent had later onset of puberty. Of boys in the high BMI group, 14 percent had later onset of puberty.
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Source: University of Michigan Health System