Theory-based digital intervention to promote weight loss and weight loss maintenance (Choosing Health): protocol for a randomised controlled trial

Dominika Kwasnicka, Aleksandra Luszczynska, Martin S. Hagger, Eleanor Quested, Sherry L. Pagoto, Peter Verboon, Suzanne Robinson, Anna Januszewicz, Paulina Idziak, Iga Palacz, Felix Naughton

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INTRODUCTION: Digital behavioural weight loss interventions have the potential to improve public health; however, these interventions are often not adequately tailored to the needs of the participants. This is the protocol for a trial that aims to determine the effectiveness and cost-effectiveness of the Choosing Health programme as a means to promote weight loss and weight loss maintenance among overweight/obese adults. METHODS AND ANALYSIS: The proposed study is a two-group randomised controlled trial with a nested interrupted time series (ITS) within-person design. Participants (n=285) will be randomly assigned to either the Choosing Health digital intervention or a control group. For intervention participants, ecological momentary assessment will be used to identify behavioural determinants for each individual in order to tailor evidence-based behaviour change techniques and intervention content.Control group participants will receive non-tailored weight loss advice via e-book and generic emails. The primary outcome is the mean difference in weight loss between groups at 6 months controlled for baseline. Secondary outcomes include blood pressure and percentage of body fat; self-reported measures of physical activity, sitting time, quality of life, cost and theory-derived correlates of weight loss. Secondary outcomes will be measured at baseline, 3, 6 and 12 months. The primary outcome for ITS will be daily weight loss plan adherence. Data will be analysed using regression and time series analyses. ETHICS AND DISSEMINATION: Ethics approval was granted by Faculty of Psychology, SWPS University of Social Sciences and Humanities, Wroclaw, Poland, approval number 03/P/12/2019. The project results will be disseminated through structured strategy implemented in collaboration with the Ministry of Health. TRIAL REGISTRATION DETAILS: This trial was registered with; registration number NCT04291482.

Original languageEnglish
Article numbere040183
Pages (from-to)e040183
JournalBMJ Open
Issue number11
Publication statusPublished - 23 Nov 2020


  • nutrition & dietetics
  • preventive medicine
  • public health

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