Abstract
Sexual dimorphism in adiposity is well described in adults, but the age at which differences first manifest is uncertain. Using a prospective cohort, we describe longitudinal changes in directly measured adiposity and intrahepatocellular lipid (IHCL) in relation to sex in healthy term infants. At median ages of 13 and 63 days, infants underwent quantification of adipose tissue depots by whole-body magnetic resonance imaging and measurement of IHCL by in vivo proton magnetic resonance spectroscopy. Longitudinal data were obtained from 70 infants (40 boys and 30 girls). In the neonatal period girls are more adipose in relation to body size than boys. At follow-up (median age 63 days), girls remained significantly more adipose. The greater relative adiposity that characterises girls is explained by more subcutaneous adipose tissue and this becomes increasingly apparent by follow-up. No significant sex differences were seen in IHCL. Sex-specific differences in infant adipose tissue distribution are in keeping with those described in later life, and suggest that sexual dimorphism in adiposity is established in early infancy.
Highlights
Sexual dimorphism in adipose tissue distribution and intrahepatocellular lipid (IHCL) are well described in adults.[1,2] Adipose tissue distribution, the accumulation of internal abdominal (IA) adipose tissue is strongly associated with cardiovascular and metabolic disease in adults[3] and children.[5]
No sex-specific differences in IHCL were detectable at baseline or follow-up. In this longitudinal cohort of healthy term babies, that sex-specific differences in total adiposity are present from shortly after birth. These differences become more pronounced by 2–3 months by which time a difference in adipose tissue distribution, characterised by higher subcutaneous adipose tissue volumes in girls, is detectable
The greater relative adiposity in girls compared with boys is in keeping with recognised sex differences,[16,17] but to our best knowledge a sex difference in adipose tissue distribution in early infancy has not been described previously in longitudinal measurements
Summary
Sexual dimorphism in adipose tissue distribution and intrahepatocellular lipid (IHCL) are well described in adults.[1,2] Adipose tissue distribution, the accumulation of internal abdominal (IA) (or visceral) adipose tissue is strongly associated with cardiovascular and metabolic disease in adults[3] (especially adult men4) and children.[5] The age at which sex differences in the distribution of adiposity begin to manifest remains unclear. Sex differences are established in adolescent,[6] pre-adolescent[7] and pre-school children,[8] implicating early childhood or infancy as the period of divergence, there is a paucity of data describing adipose tissue distribution early in life. We describe the longitudinal changes in directly measured adiposity and hepatic lipid that occur between birth and 2–3 months in healthy term babies in relation to infant sex
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