The percentage of obese individuals in the population has increased exponentially over the last decade, making obesity a phenomenon of significant global concern. Individual behaviors, preferences and lifestyle choices are subject to social and environmental influences and social networks have been identified as a key contributor to the global obesity epidemic. Numerous empirical studies have found a relationship between dimensions of social capital, well-being and population health. It is the thesis of this article that social capital in online social networks might be similarly associated. Addressing previously identified gaps in the literature, our conceptual model enables the analysis of the relationships between the structure and content of an individual's online social network, the resulting opportunities and limitations to accessing resources and his or her health-related behaviors and body weight is introduced. Moreover, the model incorporates potential social capital as a special type of social capital in online social networks and uses network-based measures instead of self-reported data. Additionally, literaturebased hypotheses discussing the relationships between the constructs of the model are presented. Establishing profound theoretical groundwork, this article encourages future research crossing the boundaries between information systems, health informatics and sociology. This study concludes by proposing a new Facebook e-health application to collect longitudinal data using the aforementioned conceptual model in order to explore the presented ideas further.

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Consumer health informatics is a relatively new and rapidly expanding area within the fi eld of medical informatics. Central to this discipline is the importance of providing information and support to individuals (consumers) so that they can be empowered and take a central role in their own health and well-being.The rapidly increasing prevalence of obesity is a phenomenon often referred to as the "obesity epidemic" (Obesity: preventing and managing the global epidemic. Report of a WHO Consultation. WHO Technical Report Series 894, WHO, Geneva, 2000). Literature suggests social networks to be one of the most important dimension of people's social environment that may enable or constrain the adoption of health-promoting behaviors (e.g., The New England Journal of Medicine, 357:370-379, 2007; Social Science & Medicine (1982), 63:1011-1022, 2006. Using data collected in qualitative interviews and via a Facebook application, this research in progress provides fi rst insights on the relationship between online social connections, health-related behaviors, and body weight.An outlook is given on how the use of online social networks may facilitate appropriate health-related behaviors in the context of obesity.