(1) The evidence base
The systematic review results identifying the evidence base that laid the foundation for intervention development are reported in detail elsewhere  and summarised briefly in this section. Despite evidence of effectiveness of workplace-based interventions to change nurses’ eating and activity behaviours, the available evidence base was limited in quality and quantity. Several important gaps were noted which caused uncertainty in establishing what intervention content and characteristics contributed most to intervention effectiveness. Additionally, few interventions to change nurses’ eating and physical activity were underpinned by a coherent theoretical framework or formative research.
(2) Theoretical determinants of nurses’ eating and physical activity behaviour
Details of the qualitative interview study are reported elsewhere . In summary, across the 16 qualitative interviews and 245 survey responses, the three most important barriers to nurses’ eating and physical activity behaviour change related to environmental context and resource factors such as time and the food environment, emotional factors such as mood and stress and behavioural regulation factors such as lack of self-monitoring and planning. The three most important enablers identified were knowledge of relevant guidelines and strategies for changing eating and physical activity behaviour, optimism about likely outcomes of behaviour change attempts and beliefs about the likely positive consequences of healthy eating and physical activity.
(3) Intervention options
Nine intervention functions and seven policy categories from the BCW were identified as having potential to bring about eating and physical activity behaviour change in nurses (Table 1; Table 2).
Based on BCTs previously judged by a consensus of four experts in behaviour change to be appropriate for changing each selected intervention function , 89 BCT’s likely to be suitable to change the identified determinants were initially considered for selection. Guided by a previous expert rating study , 22 out of the possible 89 BCTs were selected as those most likely to be effective in changing the factors identified in the qualitative interviews / survey as likely determinants of nurses’ eating and physical activity (Table 3). Additionally, it was found that certain combinations of BCTs may interact with each other to amplify or reduce effectiveness. For example, the evidence suggests that Self-monitoring of behaviour and subsequent Feedback are a typically effective combination of BCTs. However, the BCT: Threat (future punishment) may include fear arousal is likely to be counter effective when self-efficacy is low. There were insufficient studies retrieved that examined which specific BCTs or BCT combinations were most effective for distinct target populations and settings.
Further information about the selected BCTs is outlined in detail within Additional file 1.
Table 4 contains a full description of the proposed (or suggested) intervention components. It summarises the theoretical determinants of nurses’ eating and activity behaviours, the BCTs likely to be able to change these determinants and how these techniques may be translated in practice. The intervention is multi-modal, involving a combination of digital and printed modes of delivery. A multi-modal approach to intervention delivery was adopted as it is more likely to enhance effectiveness and appeal to a wider range of nurse preferences. The completed TIDieR checklist also provides further details about BCT operationalisation examples including the number, duration, intensity, and dose of the digital sessions (Additional file 2). A brief summary of the proposed intervention that arose from the systematic step-wise process adopted in the current study is presented below. This scenario represents the result of a creative process using the TDF, BCW and BCTTv1.
Nurses would have access to an online programme with a personal page consisting of five modules. Module 1 contains recommendations on avoidance/changing exposure to cues for eating and physical activity behaviour such as determining appropriate servings in advance when eating (BCT: Avoidance/changing exposure to cues for the behaviour). It could also include nurses keeping a record of unhealthy snacking/physical inactivity on their personal page (BCT: Self-monitoring of behaviour). Module 2 prompts nurses to imagine and compare likely or possible outcomes following eating healthily/participating in physical activity versus not performing these behaviours (BCT: Comparative imaging of future outcomes), invites nurses to undertake a fitness and strength test (BCT: Biofeedback) and identify situations or events occurring prior to unhealthy snacking/physical inactivity (BCT: Antecedents). Nurses would be advised to track their mood alongside their eating and physical activity behaviours on personal page of online-based programme so as to identify the emotional consequences of healthy and unhealthy behaviours for themselves (BCT: Information about emotional consequences). Lastly, module 2 would also incorporate information to increase the personal salience of the consequences of unhealthy eating and physical activity behaviours (BCT: Salience of consequences).
Module 3 contains an expert video discussing the use of stress management techniques such as progressive muscular relaxation and diaphragmatic breathing to help nurses manage their stress (BCT: reduce negative emotions). A registered dietitian/nutritionist/physiotherapist would also provide feedback within a motivational interviewing session on healthy eating/physical activity progress (BCT: Feedback on behaviour; BCT: Vicarious reinforcement) and verbally persuaded to enhance self-efficacy (BCT: Verbal persuasion to boost self-efficacy). The motivational interviewing session would also entail nurses providing their level of agreement/disagreement with the following two statements (“If I did not eat healthily and participate in physical activity I would later feel regret”) and (“If I did not eat healthily and participate in physical activity, I would later wish I had”) (BCT: Anticipated regret). Further, nurses would be advised to record how they feel after eating healthily/participating in physical activity on personal page of Module 4 (BCT: Self-assessment of affective consequences) undertake a fitness and strength test and record how they feel after eating healthily/participating in physical activity (BCT: information about emotional consequences).
Module 5 contains forum and discussion pages for peer to peer social support (BCT: social support (emotional)). In addition, nurses would be invited to attend online group motivational interviewing sessions to boost self-efficacy (BCT: Verbal persuasion to boost self-efficacy). Prior to each session, nurses would be requested to self-monitor eating and physical activity behaviours (BCT: Self-monitoring of behaviour). Similarly, at a separate online group session nurses would be requested to describe and compare the advantages and disadvantages of eating healthy/physical activity participation (BCT: Pros and cons).
Coupled with digital intervention delivery, the workplace physical environment would also be restructured by the following evidence-based strategies; placing vinyl footsteps on hospital floors to promote stair walking (BCT: Restructuring the physical environment), smaller portion sizes would be provided in the hospital canteen and food would be calorie labelled at the point of purchase (BCT: Prompts/cues). Nurses could also be advised about entry to a draw for a non-monetary incentive for taking the stairs during the working day but not the lift (BCT: Discriminative (learned) cue). A brief message about the increased risk of chronic disease following unhealthy dietary/physical activity patterns could placed on distributed pedometers in conjunction with advice on how to mitigate this risk (BCT: Information about health consequences) To restructure the social environment, social norm messages via a social marketing campaign would be implemented (BCT: Restructuring the social environment). Social marketing campaign involving a fear appeal message in combination with a self-affirmation message would also be implemented (BCT: Threat (future punishment)). A logo would be professionally created and utilised across all intervention components to promote the intervention. A web-based staff newsletter and social media used for communicating information about social and environmental consequences of healthy eating and physical activity would also be implemented (BCT: Information about social and environmental consequences).