Abstract

Background: Sustainable diets are healthy dietary patterns with low environmental impact, that are economically fair and affordable. This study aimed to evaluate the feasibility, acceptability, and potential impact of a pilot blended digital intervention aimed at promoting behavior change towards sustainable diets. Methods: We conducted a series of ABA (A phase: 2-week baseline evaluation; B phase: 22-week intervention; A phase: 24-week post-intervention, follow-up) N-of-1 trials over a year. Intervention involved (i) text messages containing brief educational information, motivational messages or links to recipes, and (ii) individualized online feedback sessions. Intensive longitudinal quantitative data on eating behaviors were collected daily for 15 weeks distributed over the year. A weekly composite score for sustainable diets was calculated to evaluate changes in the overall dietary quality, considering health and environmental sustainability. Qualitative data was collected through three individual semi-structured interviews: at baseline, at the end of the intervention, and 6 months later, to gain further insight into the study objectives. Analyses were performed at both the group and individual levels.Results: This pilot trial involved 12 participants. Feasibility and acceptability were high, with a 100% retention rate over a year, 75% attendance at all feedback sessions, and an average response rate of 86% to the intensive longitudinal eating behavior questionnaires. At the group level, the intervention had a positive and significant effect on the overall diet composition. Compared to baseline, and on a 10-point scale, participants showed a significant increase of 1.25 and 1.85 points during the intervention and follow-up phases, respectively. At the individual level, 92% of the participants demonstrated a significant increase in daily fruit and vegetable consumption between the baseline and follow-up phases, and 58% significantly reduced their intake of red and processed meat as well as ultra-processed foods. Beyond diet composition, participants reported improvements in other crucial aspects of sustainable diets, including reducing food waste, opting for minimally packaged and in-season foods, and prioritizing food from fair sources, as assessed with the qualitative interviews.Conclusion: This pilot study provides valuable knowledge for designing, optimizing, and implementing future large-scale interventions targeting individual behavior change for sustainable diets in a holistic way.