This cohort difference-in-differences study examined whether Phase 1 of Chile's 2016 Food Labelling and Advertising Law (FLAL) — featuring black octagonal front-of-package warning labels plus marketing and school restrictions — causally reduced excess weight (overweight or obesity) in children aged 4–6 years across public and subsidised schools nationwide (2012–2017).
After 18 months of exposure (kindergarten + first grade), girls had a **2.85% lower probability** of excess weight (95% CI −4.07% to −1.63%) and boys had a **2.40% lower probability** (95% CI −3.58% to −1.22%). Even 6 months of exposure (first grade only) yielded significant reductions: 1.91% for girls and 2.24% for boys.
- Observational design (difference-in-differences) can only establish plausible, not definitive, causality. - Analysis relies on administrative BMI data from public/subsidised schools, which may not represent private-school or out-of-school children. - Phase 1 thresholds for critical nutrients were later increased; longer-term or higher-dose effects are not captured.
Comprehensive food environment laws combining front-of-package warning labels with marketing and school restrictions can meaningfully reduce childhood excess weight at a population level. Policy makers should consider multi-component food labelling laws as a scalable, low-cost strategy against childhood obesity — effects are detectable within as little as 6 months of exposure.
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