Physical Activity for Health Group, School of Psychological Sciences and Health, University of Strathclyde, Glasgow, UK. Scottish Collaboration for Public Health Research and Policy, School of Health in Social Science, University of Edinburgh, UK. School of Education, University of Strathclyde, Glasgow, UK. Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium. Department of Sport and Exercise Sciences, Durham University, Durham, UK. Department of Nutrition and Dietetics, School of Health Science and Education, Harokopio University, Athens, Greece.