A Service of Leibniz-Informationszentrum econstor Wirtschaft Leibniz Information Centre Make Your Publications Visible. zbw for Economics Mata, Jutta; Richter, David; Schneider, Thorsten; Hertwig, Ralph Working Paper How cohabitation, marriage, separation and divorce influence BMI: A prospective panel study SOEPpapers on Multidisciplinary Panel Data Research, No. 973 Provided in Cooperation with: German Institute for Economic Research (DIW Berlin) Suggested Citation: Mata, Jutta; Richter, David; Schneider, Thorsten; Hertwig, Ralph (2018) : How cohabitation, marriage, separation and divorce influence BMI: A prospective panel study, SOEPpapers on Multidisciplinary Panel Data Research, No. 973, Deutsches Institut für Wirtschaftsforschung (DIW), Berlin This Version is available at: http://hdl.handle.net/10419/181026 Standard-Nutzungsbedingungen: Terms of use: Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Documents in EconStor may be saved and copied for your Zwecken und zum Privatgebrauch gespeichert und kopiert werden. personal and scholarly purposes. 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Research disseminated by DIW Berlin may include views on public policy issues, but the institute itself takes no institutional policy positions. The SOEPpapers are available at http://www.diw.de/soeppapers Editors: Jan Goebel (Spatial Economics) Stefan Liebig (Sociology) David Richter (Psychology) Carsten Schröder (Public Economics) Jürgen Schupp (Sociology) Conchita D’Ambrosio (Public Economics, DIW Research Fellow) Denis Gerstorf (Psychology, DIW Research Fellow) Elke Holst (Gender Studies, DIW Research Director) Martin Kroh (Political Science, Survey Methodology) Jörg-Peter Schräpler (Survey Methodology, DIW Research Fellow) Thomas Siedler (Empirical Economics, DIW Research Fellow) C. Katharina Spieß (Education and Family Economics) Gert G. Wagner (Social Sciences) ISSN: 1864-6689 (online) German Socio-Economic Panel (SOEP) DIW Berlin Mohrenstrasse 58 10117 Berlin, Germany Contact: [email protected] In press: Health Psychology How Cohabitation, Marriage, Separation and Divorce Influence BMI: A Prospective Panel Study Jutta Mata Health Psychology, Department of Social Sciences, University of Mannheim, Germany, and Center for Adaptive Rationality, Max Planck Institute for Human Development, Berlin, Germany David Richter German Institute for Economic Research (DIW Berlin), Berlin, Germany Thorsten Schneider Institute of Sociology, University of Leipzig, Germany Ralph Hertwig Center for Adaptive Rationality, Max Planck Institute for Human Development, Berlin, Germany © 2018, American Psychological Association. This paper is not the copy of record and may not exactly replicate the final, authoritative version of the article. Please do not copy or cite without authors permission. The final article will be available, upon publication, via its DOI: 10.1037/hea0000654 Author Note Correspondence concerning this article should be addressed to Jutta Mata, University of Mannheim, Health Psychology, L13, 17, 68131 Mannheim, Germany. E-mail: mata@uni- mannheim.de We are grateful to Susannah Goss, Lena Haas, Petra Kühner-Knaup, Emelie Letzsch, and Nicole Engelhardt. The authors declare no conflict of interest. Abstract Objective: This study examines how changes in cohabitation or marital status affect Body Mass Index (BMI) over time in a large representative sample. Methods: Participants were 20,950 individuals (50% female; 19 to 100 years), representative of the German population, who provided 81,926 observations over 16 years. Face-to-face interviews were used to obtain demographic data, including cohabitation and marital status, height, body weight, and weight-relevant behaviors (exercise, healthy eating, and smoking). Control variables included age, notable changes in status (life events such as having children or change in employment status), perceived stress, and subjective health. Results: Cohabitation led to significant weight gain in men and women—after four years or longer, about twice the gain associated with marriage (controlling for weight-related behaviors, age, children, employment, stress, and health). BMI after separation was largely comparable to BMI before starting cohabitation; women lost some weight in the first year, men gained some weight after four or more years of separation. Divorce generally predicted weight gain. Changes in exercise, healthy eating, and smoking did not attenuate the effect of changes in relationship status on BMI. Conclusions: This is one of the first longitudinal studies to directly compare the effects of key changes in relationship status on BMI. The findings extend and qualify previous results by showing that the benefits of marriage or cohabitation do not necessarily include a healthier BMI. They also suggest that relationship transitions—particularly moving in with a partner and divorce—may be important time windows for weight gain prevention. Keywords: obesity, marriage, divorce, health, longitudinal 2 Social relationships influence body weight and obesity (Christakis & Fowler, 2007). Two major relationship transitions that most adults experience are moving in with a partner and getting married (Kreider & Ellis, 2011). Several longitudinal studies suggest that particularly getting married (e.g., Gallo, Troxel, Matthews, & Kuller, 2003; Kiecolt-Glaser & Newton, 2001), but also starting to cohabit (Kohn & Averett, 2014; Musick & Bumpass, 2012), is beneficial for general health. In contrast, separating from a partner or divorcing has detrimental health effects (e.g., Sbarra, Law, & Portley, 2011). However, less is known about how these relationship transitions affect body weight, an important indicator of general health. According to the marriage market hypothesis, individuals who are no longer on the marriage market, and thus no longer concerned with attracting a mate, gain weight (e.g., Meltzer, Novak, McNulty, Butler, & Karney, 2013). Following the same logic, divorcees strive to lose weight when they re-enter the marriage market (Averett, Sikora, & Argys, 2008; Lundborg, Nystedt, & Lindgren, 2007). This hypothesis makes no explicit predictions about the effects of starting or ending cohabitation. Some authors suggest that cohabitation has similar effects on health as marriage (Kohn & Averett, 2014; Musick & Bumpass, 2012); others suggest qualitatively different effects (e.g., Marcussen, 2005). Most empirical studies on the relation between marital transitions and BMI support the marriage market hypothesis. A review of longitudinal studies examining marital transitions and changes in BMI (Dinour, Leung, Tripicchio, Khan, & Yeh, 2012) found that six of 13 studies reported weight increases for both genders after marriage, five reported increases for one gender only, and two reported no weight change. Three of four studies examining weight changes after starting cohabitation showed increased risks of weight gain. Findings for weight changes after divorce were mixed: Two of 12 studies reported weight loss in both genders, eight reported weight loss in one gender, and two reported no weight change. Only one study has examined the effects of ending cohabitation