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Modeling the influence of social networks and environment on energy balance and obesity. P Giabbanelli, A Alimadad, V Dabbaghian, DT Finegood. ICO, Stockholm July 14, 2010. Social Network Analysis. Obesity can spread through social networks. Christakis and Fowler. NEJM 357: 370, 2007.
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Modeling the influence of social networks and environment on energy balance and obesity P Giabbanelli, A Alimadad, V Dabbaghian, DT Finegood ICO, Stockholm July 14, 2010
Social Network Analysis • Obesity can spread through social networks Christakis and Fowler. NEJM 357: 370, 2007
Social Network Simulations • Traditional interventions fail because they target individuals without consideration of their social network. • Dieting with friends is ineffective compared to dieting with friends of friends. Bahr et al. Obesity (2009) 17, 723–728.
What spreads? Outcome or behaviour • Previous studies have only considered the spread of obesity. • Body weight is the product of food and physical activity related behaviours. • Social network effects are only one type of environmental influence on food and physical activity behaviour. • Marketing, the built environment, agricultural policy and many other factors also influence behaviour.
Objective • To investigate the impact of social network and environmental influences on physical activity and energy intake.
Social Network and Environmental Influences on Physical Activity
Network’s Influence where • C is either physical activity (PA) or energy intake (EI) • F is an individual’s set of friends
Social Network and Environmental Influences on Physical Activity
Change in Physical Activity where: • I is the impact on physical activity (PA) • T is the threshold that needs to be achieved to trigger change
Simulations • To identify the relative contributions of specific factors we used a factorial design that tested all combinations of low and high values for: • Environmental influence (Env) • Thresholds for changing PA and EI (TPA, TEI) • The impact on changing PA and EI if the threshold is exceeded (IPA, IEI) • and network topology (small world, scale free)
Conclusion • Individuals are influenced by both their environment and their social network with a similar order of magnitude. • While social network influences are important to changes in weight status, they should not be considered independent of other biological and environmental factors.
Acknowledgement • This works was supported by the Canadian Institutes of Health Research (MT-10574) and the Modeling of Complex Social Systems Program (MoCSSy) at Simon Fraser University.