School-based interventions encouraging children to replace sugar-sweetened beverages (SSBs) with water show promise for reducing child overweight. However, students with child food insecurity (CFI) may not respond to nutrition interventions like children who are food-secure.

The Water First cluster randomized trial found that school water access and promotion prevented child overweight and increased water intake. This secondary analysis used mixed-effects regression to evaluate the interaction between the Water First intervention and food insecurity, measured using the Child Food Security Assessment, on child weight status (anthropometric measurements) and dietary intake (student 24-hour recalls).

Eighteen elementary schools (serving ≤ 50% children from low-income households), in which drinking water had not been previously promoted, in the San Francisco Bay Area.

Students in fourth-grade classes (n=1056).

Food insecurity interacted with the intervention. Among students with no CFI, the intervention group had a lower prevalence of obesity from baseline to 7 months (-0.04, confidence interval [CI] -0.08 to 0.01) compared to no CFI controls (0.01, CI -0.01 to 0.04) (p=0.04). Among students with high CFI, the intervention group had a pronounced increase in the volume of water consumed between baseline and 7 months (86.2%, CI 21.7 to 185.0%) compared to high CFI controls (-13.6%, CI -45.3 to 36.6%) (p=0.02).

Addressing food insecurity in the design of water promotion interventions may enhance the benefit to children, reducing the prevalence of obesity.