Lifestyle behaviors such as increased private car use, stress, low physical activity, and unhealthy eating negatively affect individual and global health, environment and economy. We must change behavior, not only to decrease suffering and economical costs, but to promote wellbeing for flourishing human beings on a living planet. It may not be simple to change ingrained behaviors. Nevertheless, with aid from interventions, the success rate for behavioral change is high, yet not automatically lasting. Despite growing harm, and that brief change generates brief effects, research on maintained intervention-induced behavior is scarce. Due to this research gap, this thesis aims to broaden understanding of psychological mechanisms involved in health- and lifestyle-related intervention-induced behavior and maintenance and suggest potential development for intervention initiators and participants. The aim is approached through three field studies: Study I uses a quantitative approach to investigate motives for intervention participation, as well as psychological mechanisms in early phases of behavior adoption, in relation to immediate behavior change in a travel-intervention setting using incentives. Study II uses a quantitative approach to investigate psychological mechanisms in adopting and maintaining behavior in a mandatory, wellbeing intervention setting. Study III uses a mixed-methods approach to investigate psychological mechanisms on a deeper level, in a fee-based lifestyle intervention. For maintained intervention-induced behavioral change, the main findings indicate the importance of: Focusing on behavior goals; undergoing positive experiences during an intervention; experiencing gains from immediate outcomes; and learning to apply a flexible approach that meets shifting conditions and responses through the different intervention phases.

Lifestyle behaviors such as increased private car use, stress, low physical activity, and unhealthy eating negatively affect individual and global health, environment and economy. We must change, not only to decrease suffering and economical costs, but to promote wellbeing for flourishing human beings on a living planet. It is not simple to change ingrained behaviors, but the success rate for behavior change interventions is high, yet not automatically lasting. Despite growing problems and brief change generating brief effects, research on maintained intervention-induced behavior is scarce. Due to this research gap, this thesis aims to broaden understanding of psychological mechanisms involved in maintained lifestyle-related intervention-induced behavior and suggest potential development for initiators and participants. This aim is approached through three field studies involving travel behavior, wellbeing activities, physical activity and healthy eating. 

For maintained intervention-induced behavior change, the main findings imply the importance of: Focusing on behavior goals; undergoing positive experiences during an intervention; experiencing gains from immediate outcomes; and learning to apply a flexible approach meeting shifting conditions throughout the intervention phases.