1. Investigating obesity related behaviours in friendship networks among the youth: a systemized review
Noor Alsayed
Dr.Tillal Eldabi
Prof.Habin Lee

2. Agenda Introduction Background Literature Review Conclusion
Aim & Method
Findings
Characteristics of the reviewed studies
Associations between friendship networks and diet
Associations between friendship networks and physical activity
Associations between friendship networks and sedentary behaviour
Conclusion
Recommendations

3. Introduction
Obesity is complex because it is caused by multiple factors.
In the last three decades, our lifestyles have changed:
Calorie dense diet
Low levels of physical activity
High levels of sedentary behaviour (tv, video games, smart phones, etc)
The current preventative measures are individually targeted.
The term social networks refer to a set of individuals and the ties among them.

4. Background
Social influence theories propose that health behaviour is influenced by the individual’s social surrounding through different mechanisms including: imitation, peer modelling and social learning.
Social influence was also found to vary based on the intensity of the relationship, with close friends having more influence on an individual’s.
Much of the research in obesity has explored the role of social networks in promoting health through social influence. In comparison less research has examined how social networks themselves may be structured by health.

5. Background
Understanding the complex structure of friendship ties and examining the individual’s position in the network and their association with behaviour provides valuable insight for how to modify these behaviours.
Network size: poor health is found to be negatively associated with network size among adolescents.
Network density: dense networks have more pathways which allow attitudes and behaviours to flow.
Individual popularity: popularity is found to be positively associated with some health risk behaviours.
Individual centrality: central people are found highly influential in group behaviours

6. Literature Review
Aim: to synthesize existing literature on obesity related behaviours in friendship networks among the youth.
Method:
A systemized review of the literature was undertaken.
A systematized review encompasses multiple, but not all aspects of a complete systematic review (Grant and Booth, 2009).
Keywords: social networks, friendship networks, friends, peers, obesity, diet, eating, physical activity, exercise, sedentary behaviour, screen time

7. Findings: characteristics of the reviewed studies
A total of(n=14) met the inclusion criteria.
The included studies were interested mainly in adolescents between the ages 12 to 18 (n=12), young adults aged 19 (n=1) and children between the ages 8 to 12 (n=1).
The types of studies included literature review studies (n=2), primary data studies (n=9) and secondary data studies (n=3).
Some of the studies followed a cross-sectional study design (n=7) and others followed a longitudinal study design (n=5).
The majority of the studies employed quantitative methods (n=10), and the remaining studies used mixed methods, employing both quantitative and qualitative instruments (n=2).
The geographical locations of the studies were USA (n=6), Australia (n=4), Canada (n=2), United Kingdom (n=1) and Sweden (n=1).
Should I get rid of this slide?

8. Main themes Obesity related behaviours: Friendship networks:
Dietary behaviours
Physical activity
Sedentary behaviours
Friendship networks:
Associations between individual behaviour and friends behaviours (i.e similarities in individual’s and friends’ behaviours)
Associations between individual behaviour and characteristics/properties of friendship networks

9. Findings: Diet in friendship networks
There seems to be mixed evidence on peer and friends influences on individuals’ diet in the literature where some researchers found evidence on fast food consumption (Ali, Amialchuk and Heiland, 2011; de la Haye et al., 2010) while others did not find consistent evidence of peer or friend influence on individuals’ dietary habits (Finnerty et al., 2009; Geller et al., 2013).
Among adolescents, individual popularity (i.e receiving ties) was found to be positively associated with consumption of unhealthy snacks among males so popular boys were the highest consumers of unhealthy snacks (de la Haye et al., 2010).

10. Findings: Physical activity in friendship networks
Friends’ physical activity levels have a major influence on individual’s physical activity levels (Ali, Amialchuk and Heiland, 2011; de la Haye et al., 2011; Garcia et al., 2016 ; Sawka et al., 2013).
The proportion of active close friends was found to be positively associated with physical activity (Sawka et al., 2014).
The size of children/adolescents’ friendship groups was found to be positively associated with physical activity (de la Haye et al., 2010).

11. Findings: Sedentary behaviour in friendship networks
Evidence surrounding friendship influence on individual sedentary behaviour is limited and mixed (Ali, Amialchuk and Heiland, 2011; Sawka et al., 2013).
Network density was associated with sedentary behaviour among boys so boys in dense networks were found to be highly sedentary (Sawka et al., 2014)

12. Conclusion
The literature suggests that friendships are an important context for obesity related behaviours (de la Haye et al., 2010).
Friendships networks have been linked to obesity related behaviours; however, network characteristics have not been extensively examined (Sawka et al., 2014).
Results from this review are informative for designing effective interventions that could utilize the influence of friends to increase physical activity levels among children, adolescents and young adults.

13. Recommendations
Future studies in different cultural contexts and different clinical samples are required (Tonetti et al., 2014).
Future studies should investigate whether friendship networks influence obesity via other pathways (Ali, Amialchuk and Heiland, 2011).
Further investigation of the types of associations between networks and some of the obesity related behaviours is needed to advance our knowledge of the mechanisms of these behaviours and to inform evidence-based health intervention policies (Marks et al., 2015).

14. Questions?