Scale up of a multi-strategic intervention to increase implementation of a school healthy canteen policy: findings of an intervention trial

Background: Implementation interventions delivered in schools to improve food provision have been found to improve student diet and reduce child obesity risk. If the health benefits of food availability policies are to be realised, interventions that are effective need to be implemented at scale, across an entire population of schools. This study aims to assess the potential effectiveness of an intervention in increasing the implementation, at scale, of a healthy canteen policy by Australian primary schools. Methods: A non-controlled before and after study was conducted in primary schools located in the Hunter New England region of New South Wales, Australia. Schools received a multi-component intervention adapted from a previous efficacious and cost-effective randomised control trial. The primary trial outcome was the proportion of canteen menus compliant with the state healthy canteen policy, assessed via menu audit at baseline and follow-up by dietitians. Secondary outcomes included policy reach and adoption and maintenance policy implementation. Results: Of the 173 schools eligible for inclusion in the trial, 168 provided menus at baseline and 157 menus were collected at follow-up. At follow-up, multiple imputation analysis found 35% (55/157) of schools compared to 17% (29/168) at baseline (OR = 2.8 (1.6-4.7), p = < 0.001) had menus compliant with the state healthy canteen policy. As an assessment of the impact of the intervention on policy reach, canteen manager and principal knowledge of the policy increased from 64% (n = 76) and 38% (n = 44) respectively at baseline to 69% (n = 89) and 60% (n = 70) at follow-up (p = 0.393, p = 0.026). Adoption of the policy increased from 80% (n = 93) at baseline to 90% (n = 104) at follow-up (p = 0.005) for principals, and from 86% (n = 105) to 96% (n = 124) (p = 0.0001) for canteen managers. Multiple imputation analysis showed intervention effects were maintained six-months post intervention (33% of menus compliant OR = 2.6 (1.5-4.5), p = < 0.001 compared to baseline). Conclusions: This study found school canteen compliance with a healthy food policy increased in association with a multi-strategy intervention delivered at scale. The study provides evidence for public health policy makers and practitioners regarding strategies and modes of support required to support improvement in nutrition policy implementation across entire populations of schools.