There is no consistent result in the relationship between obesity and timing of pubertal onset in boys .
Obesity may contribute to early onset of puberty in girls , while in boys , there is insufficient data .
This systematic review and meta- analysis examined the associations between obesity and puberty timing based on scientific evidence .
Age at menarche: Influences of prenatal and postnatal growth.
OBJECTIVE The objective of this study was to determine the influence of  birth weight and postnatal weight gain  on age at menarche . DESIGN , SETTING , AND PARTICIPANTS This was a prospect i ve cohort study where girls from the West Australian Pregnancy ( Raine ) Cohort Study were followed prospect ively from fetal life ( 18 wk of pregnancy ) to adolescence ( 12 - 14 yr ) . MAIN OUTCOME MEASURE Age at menarche was the main outcome measure . RESULTS Growth status at birth was judged by expected birth weight ratio ( EBW ; a ratio of observed infant 's birth weight over median birth weight appropriate for maternal age , weight , height , parity , infant sex , and gestational age ) . Postnatal growth status was judged by body mass index ( BMI ) . Both EBW ( P = 0.020 ) and BMI in childhood ( 8 yr of age ) ( P < 0.001 ) were associated with age at menarche . Menarche occurred earlier in girls with lower EBW and higher BMI . CONCLUSIONS We have demonstrated for the first time that both birth weight and weight gain in childhood are associated with age at menarche . Weight gain before birth and subsequent weight gain up to the age of 8 yr were found to have opposing influences on the timing of menarche . Lower EBW combined with higher BMI during childhood predicted early age at menarche , and this relationship existed across normal birth weight and BMI ranges
There is no consistent result in the relationship between obesity and timing of pubertal onset in boys .
Obesity may contribute to early onset of puberty in girls , while in boys , there is insufficient data .
This systematic review and meta- analysis examined the associations between obesity and puberty timing based on scientific evidence .