Background. Evidence of an association between job strain and obesity is mixed, mostly limited to small-scale studies, and does not distinguish between categories of underweight or obesity sub-classes. Objectives. To examine the association between job strain and body mass index (BMI) in a large adult population. Methods. We performed a pooled cross-sectional analysis based on individual-level data from 13 European studies resulting in a total of 161,746 participants (49% men, mean age 43.7 years). Longitudinal analysis with a median follow-up of 4 years was possible in 4 cohort studies (N=42,222). Results. Of the participants, 86,429 were normal weight (BMI 18.5 - 24.9 kg/m2), 2149 underweight (BMI 35 kg/m2) obese. In all, 27,010 (17%) participants reported job strain. In cross-sectional analyses, we found increased odds of job strain among underweight (odds ratio 1.12, 95% confidence interval 1.00 to 1.25), obese class I (1.07, 95% confidence interval 1.02 to 1.12) and classes II-III participants (1.14, 95% confidence interval 1.01 to 1.28) as compared with normalweight participants. In longitudinal analysis, both weight gain and weight loss were related to the onset of job strain during follow-up. Conclusions. In an analysis of European data, we found both weight gain and weight loss to be associated with the onset of job strain, a finding which is consistent with the 'U'-shaped cross-sectional association between job strain and BMI. ; 0 ; Corresponding authors: Solja Nyberg Finnish Institute of Occupational Health Topeliuksenkatu 41 a A, 00250 Helsinki, Finland Email: solja.nyberg@ttl.fi Tel. +358 30 474 2639 Mika Kivimaki University College London Department of Epidemiology and Public Health 1-19 Torrington Place WC1E 6BT London The UK Email: m.kivimaki@ucl.ac.uk ; info:eu-repo/semantics/published ; Authors list: Solja T. Nyberg,1 Katriina Heikkilä,1 Eleonor I. Fransson,2 3 Lars Alfredsson,2 Dirk De Bacquer,4 Jakob B. Bjorner,5 Sébastien Bonenfant,6 7 Marianne Borritz,8 Hermann Burr,9 Annalisa Casini,10 Els Clays,4 Nico Dragano,11 Raimund Erbel,12 Goedele A. Geuskens,13 Marcel Goldberg,6 7 Wendela E. Hooftman,13 Irene L. Houtman,13 Karl-Heinz Jöckel,11 France Kittel,10 Anders Knutsson,14 Markku Koskenvuo,15 Constanze Leineweber,16 Thorsten Lunau,11 Ida E.H. Madsen,5 Linda L. Magnusson Hanson,16 Michael G. Marmot,17 Martin L. Nielsen,18 Maria Nordin,19 Tuula Oksanen,20 21 Jaana Pentti,20 Reiner Rugulies,5 22 Johannes Siegrist,23 Sakari Suominen,24 25 Jussi Vahtera,20 24 26 Marianna Virtanen,1 Peter Westerholm,27 Hugo Westerlund,16 17 28 Marie Zins,6 7 Jane E. Ferrie,17 29 Töres Theorell,16 Andrew Steptoe,17 Mark Hamer,17 Archana Singh-Manoux,7 17 G. David Batty,17 30 and Mika Kivimäki1 17 31; for the IPD-Work Consortium 1. Finnish Institute of Occupational Health, Helsinki, Finland 2. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden 3. School of Health Sciences, Jönköping University, Jönköping, Sweden 4. Department of Public Health, Ghent University, Ghent, Belgium 5. National Research Centre for the Working Environment, Copenhagen, Denmark 6. Versailles-Saint Quentin University, Versailles, France 7. Inserm U1018, Centre for Research in Epidemiology and Population Health, Villejuif, France 8. Department of Occupational Medicine, Bispebjerg University Hospital, Copenhagen, Denmark 9. Centre for Maritime Health and Safety, Esbjerg, Denmark 10. School of Public Health, Université Libre de Bruxelles, Brussels, Belgium 11. Institute for Medical Informatics, Biometry, and Epidemiology, University Duisburg-Essen, Essen, Germany 12. Department of Cardiology, West-German Heart Center Essen, University Duisburg-Essen, Essen, Germany 13. TNO, Hoofddorp, The Netherlands 14. Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden 15. Department of Public Health, University of Helsinki, Helsinki, Finland 16. Stress Research Institute, Stockholm University, Stockholm, Sweden 17. Epidemiology and Public Health, University College London, London, UK 18. Department of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen, Denmark 19. Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University, Umeå, Sweden 20. Finnish Institute of Occupational Health, Turku, Finland 21. Harvard School of Public Health, Department of Society, Human Development and Health, Boston, USA 22. Department of Public Health and Department of Psychology, University of Copenhagen, Copenhagen, Denmark 23. Department of Medical Sociology, University of Düsseldorf, Düsseldorf, Germany 24. Department of Public Health, University of Turku, Turku, Finland 25. Folkhälsan Research Center, Helsinki, Finland 26. Turku University Hospital, Turku, Finland 27. Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden 28. Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden 29. School of Community and Social Medicine, University of Bristol, Bristol, UK 30. Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK 31. Department of Behavioral Sciences, University of Helsinki, Helsinki, Finland