Exclusivity of breastfeeding and body composition: learnings from the Baby-bod study

Background: This report evaluated the breastfeeding status in a Tasmanian cohort and its effects on infant and maternal anthropometry and body composition.

Methods: An observational-cohort analysis of self-reported feeding data from 175 Tasmanian mother-baby dyads (recruited via in-person contact between September 2017 and October 2019), was executed. Only mothers who were ≥ 18 years of age, who had a singleton pregnancy and were able to speak and understand English, were included in the study. Infants outside a gestational age range between 37^{+ 0} and 41^{+ 6} weeks were excluded. Infant (using Air Displacement Plethysmography) and maternal body composition was assessed at 0, 3 and 6 months. Analysis of variance with relevant statistical corrections were utilised for cross-sectional and longitudinal comparisons between non-exclusively breastfed (neBF) and exclusively breastfed (eBF) groups.

Results: Fat-free mass was significantly higher [t = 2.27, df = 98, P = 0.03, confidence interval (CI) 0.03, 0.48] in neBF infants at 6 months (5.59 ± 0.59 vs 5.33 ± 0.50 kg) despite a higher mean fat-free mass in eBF infants at birth (2.89 ± 0.34 vs 3.01 ± 0.35 kg). Weak evidence for different fat mass index trajectories was observed for eBF and neBF infants in the first 6 months of life (ANOVA, F = 2.42, df = 1.9, P = 0.09) with an inversion in fat mass index levels between 3 and 6 months. Body Mass Index (BMI) trajectories were significantly different in eBF and neBF mothers through pregnancy and the first 6 months postpartum (ANOVA, F = 5.56, df = 30.14, P = 0.01). Compared with eBF mothers, neBF mothers retained significantly less weight (t = - 2.754, df= 158, P = 0.02, CI -6.64, - 1.09) at 3 months (0.68 ± 11.69 vs 4.55 ± 6.08 kg) postpartum. Prevalence for neBF was incrementally higher in mothers with a normal BMI compared to mothers with obesity, and mothers who underwent surgical or medical intervention during birth were less likely to exclusively breastfeed.

Conclusions: Infants with different feeding patterns may display varying growth patterns in early life and sustained breastfeeding can contribute to greater postpartum maternal weight loss.