​It is difficult to evaluate the effectiveness of interventions aimed at reducing early childhood obesity using randomized trials. The study illustrates how observational data can be analyzed using causal inference methods to estimate the potential impact of behavioral “interventions” on early childhood adiposity.

Authors used longitudinal data from 1,054 children 1–5 years old enrolled in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) and followed WIC from 2008 to 2010 for a mean duration of 23 months. The data came from a random sample of WIC families living in Los Angeles County in 2008.

Findings: Adjusted mean weight-for-height Z score at the end of follow-up was 0.73 under no intervention and 0.63 for all interventions given jointly. Exclusive breastfeeding for 6 months or longer was the most effective intervention. Other interventions had little or no effect.