The heritability of weight gain in infancy: A population-based twin study

Background: Rapid weight gain during infancy is a strong predictor of childhood obesity and is affected by genetic and environmental factors. Identifying ages with low heritability will allow for targeted interventions that might be able to prevent the adverse effects of childhood obesity. Objectives: The objective of the study is to estimate the heritability of weight gain from birth to defined ages during infancy, as well as during 6-month periods from birth to 18 months of age. We address this by leveraging large-scale computerised anthropometric data from the state-run network of well-baby clinics in Israel. Methods: We performed a population-based twin study. We extracted weight measurements recorded between birth to 24 months from well-baby clinics for 9388 twin pairs born in Israel between 2011 and 2015. The reported sexes of the twins were used as a proxy for their zygosity status. We estimated the heritability of the weight z-score change from birth to specific ages and during particular periods in infancy. To assess the validity of the results, we repeated the analysis in a sub-cohort of twin pairs with complete weight measurements. Results: During the first 2 years of life, heritability was lowest for birthweight ((Figure presented.)). Heritability for weight gain since birth was highest at 4 months ((Figure presented.)), and then gradually decreased until age 18 months ((Figure presented.)). Estimating the heritability in 6-month intervals from birth to 18 months, heritability was highest during the 6–12-month interval ((Figure presented.)), and was substantially lower during the subsequent 12–18-month interval ((Figure presented.)). Conclusions: Heritability of weight gain decreases substantially in the second year of life, suggesting that this period could be an appropriate time for interventions for infants who are at an increased risk of childhood obesity.