Heavier boys more likely to hit puberty later

Which explains the small size of their, ahem, members, during those formative years.

Overweight boys may start puberty later than their leaner peers, new research shows.

The link between higher body mass index (BMI) -- a standard measure of the relationship between height and weight used to gauge how fat or thin a person is -- and earlier puberty is fairly well established in girls, Dr. Joyce M. Lee of the University of Michigan in Ann Arbor and her team note in the Archives of Pediatrics and Adolescent Medicine. However, much less research has been done on BMI and age at puberty in boys.

To investigate, they looked at 401 boys enrolled in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. The boys' height and weights had been measured at several points, beginning when they were two years old and ending when they were eleven and a half.

Lee and her colleagues divided the boys into three groups based on how quickly their BMI increased during that time span. Fourteen percent of boys in the heaviest group had not started puberty by 11 and a half, compared to around 13 percent of boys in the middle group and 8 percent of boys in the lowest BMI group.

Growth in penis size is just one part of puberty, which also includes such changes as pubic hair development, testicular growth, muscle development, and a growth spurt.

Maxi-you, meet mini-you.

Aren't they cute when they're little?