Early onset of overweight among children from low-income families: The role of exclusive breastfeeding and maternal intake of ultra-processed food.

Context: There is an increasing prevalence of overweight during early childhood in the most impoverished areas in Brazil, although there is a lack of evidence regarding its onset.

Objectives: To investigate the incidence and risk factors associated with overweight among low-income children during their first year of life.

Methods: We analysed data from a prospective birth cohort study conducted in Brazil, which followed-up children at birth, 3rd, 6th and 12th months (n = 196). The overweight incidence (zBMI/A > 2SD) was analysed using the Kaplan-Meier survival estimator and its associated factors by the Coxs regression model. Missing data were addressed with multiple imputations and results on the final adjusted model were calculated by pooling the estimates generated for each imputed dataset.

Results: The overweight incidence was 17 events/100 children-year, and most cases occurred before the 6th month. The final model showed that children exclusively breastfed up to 30 days (vs. >30 days; HR 2.68; 95%CI 1.11-6.49) and whose mothers consumed ultra-processed foods more than 4 times/day (vs. ≤4 times/day; HR 3.02; 95%CI 1.28-7.13) presented a higher risk of developing overweight.

Conclusion: The overweight incidence was high in this impoverished population. Shorter exclusive breastfeeding duration and an unhealthy household food environment provided a short-term risk increase.