Using behavioural insights to reduce sugar in primary school children's packed lunches in derby; A cluster randomised controlled trial

Children's packed lunches contain more sugar than school-provided meals. Interventions to improve the provision of healthier packed lunches have modest effects on lunch contents. This cluster randomised controlled trial tested an intervention to encourage healthier provision of packed lunches by parents of primary school children in Derby. Schools were randomised to intervention (n = 8) or control (n = 9) using blocked random allocation. In the intervention group, parents of children who brought packed lunches to school in years 3-6 (age 7-11 years) received three bundles of materials (including packed lunch planner, shopping list, information on sugar content of popular lunchbox items and suggestions for healthier swap alternatives) in bookbags/lunchboxes over a 4-week period. Control parents received no materials. Photos of lunchbox contents were taken at baseline, immediately post-intervention and at three-month follow-up. A parental survey aimed to assess capability, opportunity and motivation for packing a healthier lunchbox. No intervention effects were observed for primary outcomes (presence and number of sugary snacks or chilled sugary desserts). The intervention had a significant impact on one secondary outcome (increased number of healthier "swap" items suggested in intervention materials) immediately post-intervention, but this effect had disappeared at three-month follow-up. No intervention effects were found on survey variables. Parent comments revealed that materials were either received positively (as they reinforced existing behaviours) or negatively (as they were not perceived to be helpful or appropriate). The results of this study suggest that providing educational materials and resources to parents of primary school children in Derby was not sufficient to increase provision of healthier packed lunches. Future research should investigate how behavioural science can support families to improve the nutritional content of primary school children's lunchboxes.