Determinants of infant adiposity across the first 6 months of life: Evidence from the Baby-bod study

Excess adiposity in infancy may predispose individuals to obesity later in life. The literatureon determinants of adiposity in infants is equivocal. In this longitudinal cohort study, we investigatedpre-pregnancy, prenatal and postnatal determinants of different adiposity indices in infants, i.e.,fat mass (FM), percent FM (%FM), fat mass index (FMI) and log-log index (FM/FFMp), from birthto 6 months, using linear mixed-effects regression. Body composition was measured in 322, 174and 109 infants at birth and 3 and 6 months afterwards, respectively, utilising air displacementplethysmography. Positive associations were observed between gestation length and infant FM,maternal self-reported pre-pregnancy body mass index and infant %FM, and parity and infant%FM and FMI at birth. Surprisingly, maternal intake of iron supplements during pregnancy wasassociated with infant FM, %FM and FMI at 3 months and FM/FFMp at 6 months. Male infant sexand formula feeding were negatively associated with all adiposity indices at 6 months. In conclusion,pre-pregnancy and pregnancy factors influence adiposity during early life, and any unfavourableimpacts may be modulated postnatally via infant feeding practices. Moreover, as these associationsare dependent on the adiposity indices used, it is crucial that researchers use conceptually andstatistically robust approaches such as FM/FFMp