An Investigation of Evaluation Approaches for Dietary Digital Interventions for Improving Children's Dietary Intake

To help promote healthier eating practises in children, Public Health England launched the Change4Life Food Scanner app, which provides nutritional feedback on barcode scanned products. The aim of this thesis was to develop a framework for evaluating dietary digital interventions (DDI) in improving 4-11 year old children's dietary intake. A narrative review (Chapter 2) and content analysis of behaviour change techniques (BCTs) within the Food Scanner app (Chapter 3) were conducted to increase understanding of DDI mechanisms of behaviour change. A systematic review (Chapter 4), and stakeholder engagement (Chapter 5) explored the methodological approaches, and generated recommendations, to evaluating (cost) effectiveness of DDIs within a child population. Results informed aspects of a pilot randomised controlled trial (RCT), with feasibility and acceptability parameters, that evaluated the effectiveness (Chapter 6) and economic and health impacts (Chapter 7) of the app. Food diaries, questionnaires, healthcare resource use, and health-related quality of life measures were analysed in SPSS and STATA, whilst qualitative data was analysed thematically. There was no preliminary evidence to suggest app (cost) effectiveness in improving diet. RCT methods were considered feasible, however improved alternatives are discussed. Four recommendations for the development and evaluation of DDIs emerged. Firstly, the effectiveness of DDIs is constrained by aspects of the current food system; DDIs should form part of broader interventions to achieve food system shifts. Secondly, in the light of difficulties in generating evidence of long-term intervention effects, economic modelling may be a solution to implementing empirical evaluations. Thirdly, the app can be improved through BCT and content development. Finally, app evolution and iterative evaluation processes should be embedded within evaluation frameworks to aid DDI developments. Results can be used to aid DDI developments targeting child outcomes. Results can additionally support future evaluations of DDIs by demonstrating feasible approaches, alongside suggestions for improved methodologies.