Fat Mass Accretion from Birth to 5 Years and Metabolic Homeostasis in Childhood: the Healthy Start Study

Abstract Context It is unclear how fat mass accretion in early life is related to glucose–insulin homeostasis. Objective Examine associations of fat and fat-free mass accretion from birth to early childhood with glucose–insulin homeostasis in early childhood in a multi-ethnic cohort. Methods Observational Healthy Start study with data collection from 2010 to 2020. Air displacement plethysmography at birth and 4.8 (SD 0.7) years estimated fat mass percent (FMP, %), fat mass index (FMI, kg/m2), and fat-free mass index (FFMI, kg/m2). General population recruited from academic obstetrics clinics in Denver, Colorado, consisting of 419 mother/offspring dyads. The main outcome measures were fasting glucose, insulin, homeostasis model assessment-2 insulin resistance (HOMA2-IR), and beta-cell function (HOMA2-B) at 4.8 years. Results Greater fat mass accretion from birth to early childhood was associated with higher fasting glucose (ΔFMP β = 0.20 [95% CI 0.06-0.34], ΔFMI β = 0.90 [0.30-1.50]) in participants of Hispanic, Black, and Other races/ethnicities, while greater fat-free mass accretion was associated with higher fasting glucose in non-Hispanic White participants (ΔFFMI β = 0.76 [0.21-1.32]). Overall, greater fat, but not fat-free, mass accretion was also associated with higher insulin (ΔFMP β = 0.14 [0.09-0.18], ΔFMI 0.71 [0.51-0.92]), HOMA2-IR (FMP β = 0.02 [0.01-0.02], ΔFMI β = 0.09 [0.06-0.12]), and HOMA2-B (ΔFMP β = 0.92 [0.18-1.36], ΔFMI β = 4.76 [2.79-6.73]). Conclusion Greater fat mass accretion in infancy and childhood is associated with shifts in fasting glucose in children of Hispanic, Black, and Other races/ethnicities at 5 years of age. Body composition beginning in early life is relevant for metabolic health, and precise assessments of adiposity in pediatric research are needed.