1 Institute of Health and Society, Newcastle University, Newcastle upon Tyne NE2 4AX, UK; Fuse, The UK Clinical Research Collaboration Centre of Excellence for Translational Research in Public Health, Newcastle upon Tyne, UK. Electronic address: falko.sniehotta@ncl.ac.uk.
2 Institute of Health and Society, Newcastle University, Newcastle upon Tyne NE2 4AX, UK.
3 Research Department of Behavioural Science and Health, University College London, London, UK.
4 Primary Care Unit, Institute of Public Health, University of Cambridge, Cambridge, UK.
5 University College London Centre for Behaviour Change, University College London, London, UK.