Rising rates of obesity in young children, even at preschool ages [1], indicate that future preventative strategies against childhood and subsequent adult obesity will require the identification of their very early predictive factors. In adults, early age at menarche is a strong risk factor for increased risk of obesity in women [2–4]. However, the causal direction and mechanism behind this association are debatable, as girls with earlier menarche are more likely to be overweight even before the onset of puberty [5,6]. The link between earlier menarche and adult obesity may simply be due to their common association with previous overweight. Rapid infancy weight gain may be the common aetiological factor, as this early growth pattern is predictive for both earlier menarche and increased obesity risk [7,8]. The 1946 British National Birth Cohort showed that women with earlier menarche had rapid growth during the first 2 y of life followed by average growth rates between ages 2 through 7 y [7]. In contemporary birth cohort studies rapid infancy weight gain also predicts subsequent obesity risk in children and adults [8].
