Differences in body composition between infants of South Asian and European ancestry: the London Mother and Baby Study

Background South Asian children and adults have a more adipose body composition compared with those of European ancestry. This is thought to be related to their increased risk of metabolic disorders. However, little is known about how early in life such differences are manifest. Objective To determine whether there are differences in fat mass (FM) and fat-free mass (FFM) between UK-born South Asians and White Europeans in infancy. Design A cross-sectional study of 30 South Asian and 30 White European infants aged 6–12 weeks. Mothers were recruited from clinics in London, and infants’ FM and FFM were determined using air-displacement plethysmography (PeaPod(®)). Results In early infancy South Asians had less FFM than White Europeans [0.34 kg less, 95% confidence interval (CI): 0.15, 0.52], with a considerably weaker indication of them also having more FM (0.02 kg more, 95% CI: −0.14, 0.18). These differences persisted when the overall smaller body size of South Asian infants was taken into account. For a given total infant weight, the balance of body composition of South Asians was shifted by 0.16 kg (95% CI: 0.06, 0.25) from FFM to FM. The ethnic differences in the amount of FFM were almost completely accounted for by ethnic differences in the rate of growth in utero and length of gestation. Conclusions The characteristic differences in body composition observed between adult South Asians and White Europeans are apparent in early infancy. Of particular note is that this is the first study to demonstrate that South Asians compared with White Europeans have reduced FFM in infancy. The early manifestation of this phenotype suggests that it is either genetic and/or determined through exposure to maternal physiology, rather than a consequence of behaviours or diet in childhood or at older ages.