[A new examination of the determinants of weight in early childhood].

Introduction: In the last decades, Chile has experienced a triple transition regarding demographic, nutritional, and economic issues.

Objective: To explore the relationship between childhood weight and two dimen sions of socioeconomic status, family income, and maternal educational level, analyzing the effect of each one by itself and how they operate together to determine childhood weight and comparing their effect on obese and non-obese children.

Subjects and method: Study based on data from the 2012 Encuesta Longitudinal de Primera Infancia (Early Childhood Longitudinal Survey), evaluating children between 2 and 6 years old (n=11,399). We estimated multivariate quantile regression models for the z-score of the body mass index (BMI-z).

Results: We found that in children aged 2-3 years, income and weight had a positive association, while maternal educational level and weight had a negative one. In children aged 4-6 years, income and weight were negatively associated among chil dren whose mothers have a higher educational level but positive among those with lower educational levels.

Conclusion: Family income and maternal educational level have opposite effects on childhood weight. The positive effect of income on BMI-z is diminished when mothers have high educational levels. We recommend studying the effects of income and education on child weight separately and exploring the causal mechanisms that explain the relations between socioeconomic determinants and childhood weight.