Effects of Peru’s National School Feeding Program (Qali Warma) on Overweight and Obesity Among Children Aged 36–59 Months

Background: School feeding programs aim to improve child nutrition, and they may influence weight outcomes insofar as program modalities and household responses alter children’s total energy intake. This is especially relevant in countries facing the double burden of malnutrition, where undernutrition and micronutrient deficiencies coexist with rising overweight and obesity. This study estimates the effect of Peru’s former National School Feeding Program on obesity and excess weight among children aged 36 to 59 months under a selection-on-observables identification strategy and assesses whether impacts differ across operational modalities, particularly breakfast-only versus breakfast plus lunch and ready-to-eat rations versus foods delivered for preparation. Methods: We use repeated cross-sectional microdata from the Demographic and Health Survey (ENDES) pooled over 2014 to 2018 and link them to administrative information. The sample includes 18,959 children aged 36 to 59 months. To improve comparability, we estimate propensity score weights targeting the average treatment effect on the treated (ATT) using a machine learning generalized boosted model (GBM), and assess covariate balance using standardized mean differences and Kolmogorov–Smirnov statistics. Identification assumes conditional independence given observed covariates and overlap (common support). Main estimates rely on weighted probit models with fixed effects, progressively adding exposure duration, modality indicators, and controls. Distributional effects are examined using quantile regression on the continuous weight-for-height z-score. Results: Without differentiating modalities, beneficiary status is not associated with a statistically significant change in obesity, while pooled baseline estimates indicate a statistically significant higher probability of excess weight. Modality-specific results show that obesity declines only when Qali Warma is delivered as breakfast plus lunch through products to be prepared (approximately −1.0 percentage point in parsimonious models and −0.4 percentage points after controls). Evidence for excess weight is directionally consistent by modality but less conclusive once controls are included. Conclusions: Qali Warma’s effects on early-childhood weight outcomes depend on implementation modality. Evaluations of school feeding programs should incorporate operational heterogeneity, particularly during program redesign.