Puberty is a period of physical and psychological maturation with long-term effects on health. Over the last decades a secular trend towards earlier puberty has occurred in association with improvements in nutrition and the increasing number of obese patients.27
The rising problem of childhood obesity has stimulated growing interest in the relationship between body composition during childhood and the timing and tempo of puberty. In North America and Europe, the age at the onset of menarche has declined from the age of 17 years in the mid-19th
century to less than 14 years in the mid 20th
Similar trends have also occurred in the age at onset of thelarche and pubarche in girls.29–32
There are fewer records on the mean age at pubarche and testicular volumes changes in boys, so that data are insufficient to establish recent secular trends of pubertal onset in boys.33
Several cross-sectional studies have shown an association between increased BMI during childhood and early pubertal development in girls.29–32
Interestingly, not only childhood body size, but even early life factors might influence pubertal timing. Rapid early weight gain has been linked to elevated IGF-1 concentrations and insulin resistance, elevated adrenal androgen concentrations, exaggerated adrenarche, obesity, and consequently elevated concentrations of hormones such as leptin. It has been suggested that these factors could promote the activity of the gonadotropin-releasing hormone (GnRH) pulse generator, thereby influencing the timing of puberty.34
In particular, Terry et al.
have found that size at birth and infant weight gain from 4 months to 1 year of life are associated with earlier age at menarche in girls.35
Other studies in this field have described similar results showing additive effects of pre- and postnatal growth on timing of menarche.36–38
In contrast, the relevance of early life risk factors for pubertal timing in boys is unclear, mainly because of the lack of an easily identifiable pubertal marker. However, a large study following a birth cohort of 6873 children from 1997, has recently suggested that, infant weight growth may be associated with earlier pubertal onset even in boys.39
Whereas the majority of studies have reported an anticipation of age at pubertal onset in obese girls, for boys the evidence is less clear with conflicting results. In fact, whereas most European studies have shown that obesity is associated with earlier puberty and voice break,3,40–43
American studies have mainly reported the opposite finding of obesity being associated with delayed puberty in boys.33,44–46
These discordant findings are partially explained by the method of assessing puberty. A direct assessment of pubertal stage has been performed only in few studies, whereas others have been based on some surrogate markers of pubertal onset and progression, such as peak height velocity or age at voice break.
Furthermore, for both sexes, only few longitudinal studies have evaluated the effect of pre-pubertal body composition on pubertal onset and progression.31,43–46
The lack of longitudinal studies limits the possibility of defining the direction of the relationship between childhood obesity and pubertal maturation, in terms of which event comes first and hence influences the other. In fact, on the one hand, earlier puberty might be associated with a tendency of increasing fat deposition; whereas on the other hand, rapid weight gain might predispose to earlier puberty, but which event comes first has rarely been investigated, due to insufficient prospective studies in this field.