Too good to waste! Short-term and long-term effects of a leftover meals intervention program on household dinner food waste reduction

Household food waste is a global concern impacting the environment, society, and economy. Effective intervention strategies are needed towards households with children due to their high reported dinner food waste. This study investigates the short-term and long-term impact of a behavioural intervention on dinner food waste in households with children, discussing the behaviour-change mechanisms in light of the Comprehensive Action Determination Model framework. A randomised controlled trial was conducted with 230 Norwegian families that involved incorporating leftovers into dinners and using online learning resources for 4 weeks (intervention group). Additionally, the participants monitored their dinner food waste for 7 weeks (intervention and control groups). Short-term, both groups reduced their total waste, but the reduction was more significant in the intervention group (n = 113) than the control group (n = 117), with −39 % against −22 % in the control group. Both groups discarded less fresh fruit, bread and dairy products. The intervention group additionally discarded lower amounts of fresh vegetables, potato products and pasta. Long-term, at 52 weeks follow-up (n = 144), the difference in reduction between the groups was no longer significant. However, both groups had reduced their total food waste, indicating the sustained impact of increased awareness regarding household waste, also from mere self-reporting. Globally, the participating households reduced their dinner food waste by −29 % at week 52, equivalent to −146 g/week. These results suggest that food waste organisations and policymakers should consider combining practical and informational strategies for effective short-term waste reduction results, and highlight self-reporting as a valuable tool for triggering long-term behavioural change.