I believe the data suggests this is true for girls, but the data is inconclusive for boys.

>“We found that in mid- to late puberty, girls with greater total body fat demonstrated higher levels of some reproductive hormones including follicle-stimulating hormone (FSH), inhibin B and male-like hormones such as testosterone."

>The researchers found that girls with higher total body fat had differences in reproductive hormone levels, developed mature breasts more slowly and got their first period earlier than girls with lower total body fat.

Obesity may affect puberty timing and hormones in girls