Puberty, obesity and ethnicity.

Lay and medical sources state that children enter puberty earlier now than in past decades. Although it is clear that puberty and menarche currently begin at younger ages than they did in past centuries, a comparison of the onset of puberty during the few past decades is more difficult to interpret. African-American girls do start puberty earlier and menarche is earlier than in White girls, and the gap between the two has widened during the past 20 years. This change between ethnic groups might be due to an increasing difference in body mass index (BMI) values. Greater BMI values are associated with pubertal onset or menarche; thus, if BMI continues to increase in childhood, earlier puberty might well be found in the general population in the future. In the absence of accurate data from the past or definitive studies at present, however, it cannot be stated with assurance that puberty today starts significantly earlier than it did in the past 4-5 decades across the whole population.