Developing Theory, Evidence and Person-Based Intervention Content Targeting Sedentary Behaviour Change for People Living with Obesity

Both sedentary behaviour (SB) and obesity are independent risk factors for poor health and quality of life. Minimising SB is an important public health and population level strategy. However, people with obesity have unique and complex challenges to minimising SB which require complex multilevel interventions. Interventions are more likely to be effective and acceptable if they are theory, evidence and person-based. The overarching aim of the thesis was to develop a theoretically underpinned, evidence and person-based, complex intervention targeting change in SB for people with obesity. A mixed methods approach and two complementary frameworks, the Behaviour Change Wheel (BCW) and Person-Based Approach (PBA), were used to complete this PhD thesis. Both frameworks align to the Medical Research Councils guidelines for complex intervention development. The thesis includes 5 individual studies, conducted to meet the overarching aim of the thesis. Studies 1 and 2 both involved separate rigorous prospectively registered systematic reviews to identify the evidence for SB interventions (study 1) and for correlates of SB in the population of people who have developed obesity (study 2). Study 3 engaged an international panel of experts and SB researchers in a robust consensus process to standardise outcome measures for SB interventions. Study 4 involved a qualitative study with people with obesity using an in-depth reflexive thematic analysis and the Theoretical Domains Framework (TDF) to identify barriers and facilitators to interrupting SB in all domains of living. Study 5 used the behaviour change wheel methodology and person-based approach to integrate the findings from study 1, 2, 3, and 4 with a further secondary analysis of qualitative data collected during study 4, to develop an intervention targeting leisure time SB in the domestic domain, for people living with obesity. The results of study 1 and 2 identify a dearth of evidence regarding SB in the population living with obesity. Study 1 also identified that heterogeneity of measurement and reporting of outcomes limit the accumulation of evidence for SB interventions and that few studies are theoretically underpinned from design through implementation and evaluation. Some evidence exists that interventions specifically targeting sedentary behaviour can reduce SB by 32 minutes / day. SB should be measured using an accelerometer with inclinometer function and reported using the core outcome set developed in study 3. Regarding the population living with obesity, a complex interplay of barriers to interrupting SB exist at individual, societal, environmental and policy level and require a multi-level response to provide the capability, opportunity and motivation to reduce SB in all domains (studies 4 and 5). A shortlist of behaviour change techniques with potential to change SB in the domestic domain are identified, which can be delivered remotely via an online intervention. Intervention functions consist of education, persuasion, training and enablement. Strategies and guiding principles are outlined. Future SB intervention designers can refer also to the longlist of relevant BCTs. A theory, evidence and person-based approach to develop an intervention targeting change in SB for people living with obesity is described and illustrated for leisure time SB in the domestic domain. The BCW, COM-B model, TDF and BCT-Taxonomy provided the framework for selection of theoretical content. To ensure relevance for the target population, the content and mode of delivery was developed in collaboration with people with moderate to severe obesity using a person-based approach, while measurement of core outcomes were standardised by consensus with SB experts and researchers. This PhD thesis provides important findings and key considerations for practice, policy and research regarding SB, obesity and developing theoretically underpinned interventions.