The HAPPY trial
RECRUITMENT, RECRUITMENT
In this study, post-hoc analysis using data from the HAPPY (Healthy eating using APP technologY) Trial has been performed. The HAPPY Trial investigates a smartphone app-based intervention – the HAPPY app – the protocol for which is described in detail elsewhere [Recruitment of patients from primary healthcare centres in Stockholm, Sweden, began in January 2019 and ended in August 2022. Due to the Covid-19 pandemic, recruitment of study participants was paused during 2020–2021. Study participants received oral and written information about the trial and voluntarily gave written informed consent prior to study start. Participants were randomized 1:1, to the intervention and control group. Those in the intervention group gained access to the app-based healthy eating intervention at baseline, and also continued to receive usual care. The control group received only usual care from baseline to 3 months, after which access to the app was given. In this study, we have analysed the intervention effect on diet-related GHGEs from baseline to the 3-month (3m) follow up of the HAPPY Trial. As such, we explored the effects of the intervention from an environmental, rather than clinical perspective, which provides an additional outcome from those included in the original trial protocol.The intervention was designed to improve overall dietary intake according to the Swedish national dietary guidelines, with a focus mainly on dietary habits, rather than intake of specific nutrients. The intervention was delivered via an app over 12 weeks, with each week covering one topic: 1) healthy food patterns, 2) vegetable intake (reoccurring again in week 5), 3) regular eating habits, 4) sugar, 6) carbohydrates, 7) wholegrains and fibres, 8) legumes, 9) saturated fat, 10) unsaturated fat, 11) salt, and 12) beverages. Of particular relevance to the study of GHGEs, were the topics of legumes (week 8) and saturated fats (week 9) which included recommendations to reduce red and processed meat. For each week, users were provided with healthy eating behaviours to perform (e.g., increase daily vegetable intake this week). For each day of the week, users were provided with an activity in the app (e.g., recipe 1 and 2 on Tuesday; evaluation on Sunday) alongside The intervention was designed to generate dietary change based on three theories central to intervention research: the health belief model [