Adolescent Friendships, BMI, and Physical Activity: Untangling Selection and Influence Through Longitudinal Social Network Analysis

The Value of an Informal Before-School Exercise Opportunity for Adolescent Girls Living in a Low-Socioeconomic Community

BACKGROUND

Physical activity is beneficial to physical, social, and emotional well-being, and schools are required to provide opportunities to engage in physical activity. While physical education and school sport have been extensively researched, little is known about the value of informal, unstructured, exercise opportunities.

METHODS

This study involved interviews with 19 adolescent girls who attended "extra" exercise opportunities provided by their school. The 3 opportunities were: (1) informal before-school exercise sessions at school, (2) before-school sport training, and (3) externally provided exercise sessions in a community setting during school hours.

RESULTS

Students perceived all opportunities as valuable with benefits to confidence, social well-being, and emotional well-being. The informal exercise sessions held greater benefits to confidence as confidence transferred from the physical activity context into the academic classroom more so than for those participating in sport. Social benefits were greater for those exercising before school as this opportunity created new relationships with teachers and with students from other classes and year groups.

CONCLUSIONS

The opportunity to engage in informal exercise with peers before school widened social networks, increased confidence, changed the overall school climate, and increased attendance.

Disentangling associations between pubertal development, healthy activity behaviors, and sex in adolescent social networks

With the onset of puberty, youth begin to choose their social environments and develop health-promoting habits, making it a vital period to study social and biological factors contextually. An important question is how pubertal development and behaviors such as physical activity and sleep may be differentially linked with youths' friendships. Cross-sectional statistical network models that account for interpersonal dependence were used to estimate associations between three measures of pubertal development and youth friendships at two large US schools drawn from the National Longitudinal Study of Adolescent to Adult Health. Whole-network models suggest that friendships are more likely between youth with similar levels of pubertal development, physical activity, and sleep. Sex-stratified models suggest that girls' friendships are more likely given a similar age at menarche. Attention to similar pubertal timing within friendship groups may offer inclusive opportunities for tailored developmental puberty education in ways that reduce stigma and improve health behaviors.

Peer effects in weight-related behaviours of young people: A systematic literature review

Individual preferences and beliefs are perpetually shaped by environmental influences, with peers playing a key role in this dynamic process. Compelling evidence from qualitative and quantitative studies has highlighted the significant impact of peer influence on health-related decisions. This systematic literature review critically synthesises findings from 45 studies published between 2011 and 2022, providing a comprehensive understanding of the nature of peer effects on dietary, physical activity and sleep behaviours during youth. The majority of studies indicated that social norms drive directional changes in eating and physical activity. Yet, our analysis revealed a notable gap in exploring alternative mechanisms, including social comparison and social identity, despite their potential relevance. Studies, generally classified as moderate to high quality, predominantly relied on self-reported data, potentially affecting the validity and reliability of measures. Meta-regression analyses suggest a small, but significant association of sample size with the magnitude, sign and significance of the reported peer effects. Moreover, studies focusing on physical activity are more likely to report significant outcomes, whereas findings on peer influence on sleep-related studies tend to reveal less pronounced effects, compared to studies on dietary behaviours. Experimental designs do not appear to increase the likelihood of finding significant effects when compared to other study designs. In conclusion, this synthesis emphasises the need for further research into the underlying mechanisms on peer effects to better inform policy-makers in designing effective policies for improving weight-related behaviours in young people.

Understanding the relationship between social capital, health, and well-being in a southern rural population

PURPOSE

Social capital is thought to contribute to health and well-being, but its application to a rural context is poorly understood. This study seeks to examine how different forms of social capital relate to health and well-being among rural residents and the extent to which race and degree of rurality moderates these relationships.

METHODS

Data from a population-based survey of 6 counties in rural Georgia (n = 1,385) are used. We examined 3 forms of social capital (diversity of interaction, civic engagement, and voting behavior) in relation to 3 health and well-being measures (overall life satisfaction, general health status, and 30-day physical health).

FINDINGS

Interacting with more diverse social networks was associated with higher overall life satisfaction for White but not Black participants (P ≤ .001). For those living in more rural communities, interacting with a more diverse social network was more strongly associated with greater general health as compared to those who lived "in town" (P ≤ .01). Greater civic engagement and voting behavior were associated with greater general health for White but not Black participants (Ps < .05). Likewise, voting in all 3 elections was associated with greater overall life satisfaction and fewer days of poor physical health for White but not Black participants (Ps ≤ .05).

CONCLUSION

Social capital may be associated with positive health and well-being among those living in rural areas, but it may vary by race and degree of community rurality, suggesting the need to further understand how social capital operates in a rural context.

How Social Networks Influence Human Behavior: An Integrated Latent Space Approach for Differential Social Influence

How social networks influence human behavior has been an interesting topic in applied research. Existing methods often utilized scale-level behavioral data (e.g., total number of positive responses) to estimate the influence of a social network on human behavior. This study proposes a novel approach to studying social influence that utilizes item-level behavioral measures. Under the latent space modeling framework, we integrate the two latent spaces for respondents' social network data and item-level behavior measures into a single space we call 'interaction map'. The interaction map visualizes the association between the latent homophily among respondents and their item-level behaviors, revealing differential social influence effects across item-level behaviors. We also measure overall social influence by assessing the impact of the interaction map. We evaluate the properties of the proposed approach via extensive simulation studies and demonstrate the proposed approach with a real data in the context of studying how students' friendship network influences their participation in school activities.

Dynamic weight status changes and peer lifestyles in early adolescence: A social network analysis on a longitudinal cohort of Taiwanese youth

BACKGROUND

Friendship networks are relevant to adolescent weight status and lifestyle, but little is known about their relationship in an East Asian setting. Using a longitudinal cohort of Taiwanese adolescents, we studied how weight status and lifestyles might influence friendship. Simultaneously considering the influence of friendship networks, we further examined the effects of peers' lifestyles on the body weight status of adolescents.

METHODS

Data were retrieved from the first three waves of the Taiwan Youth Project (N = 2409; 51 % boys). Participants were asked to nominate their friends at school and to report their lifestyle factors (e.g. sleep habits, internet use, and athletic performance). Weight status was proxied by body mass index calculated from self-reported weight and height. Stochastic actor-based modeling was used for the friendship network analyses.

RESULTS

Considering network structure, adolescents selected friends based on similarities in weight status (β = 0.147 [standard error = 0.044], p < 0.001) and lifestyle factors, such as athletic performance (β = 0.181 [0.034], p < 0.001), internet use (β = 0.156 [0.039], p < 0.001), and social jetlag (β = 0.055 [ ± 0.022], p < 0.05). In the behavior dynamics model, we did not observe any peer influence on changes in adolescents' weight status.

CONCLUSION

These findings suggest a pervasive homophilic friendship selection explained by weight and lifestyle-based similarities, despite no evidence of peer influence on weight status. Stakeholders and care providers of adolescent health should be aware of the social network processes that underlie weight problems.

Adolescent Body Mass Index and Exposure to Peers with Overweight and Obesity: A Structural Equation Model Approach to Longitudinal Network Data

Purpose: Considerable evidence has shown that social networks influence a wide variety of health behaviors. This study investigates whether having friends with overweight/obesity in one's social network (network exposure) can predict changes in body mass index (BMI) throughout high school in a diverse urban population of students. Methods: Racially and ethnically diverse students from five high schools in Los Angeles County were surveyed at four time points throughout high school from 2010 to 2013 (N = 2091). Surveys included questions on students' social networks, demographics, and health-related information. BMI and weight categories were calculated for all students who provided height and weight information (∼50%). A latent growth curve model was used to assess the growth trajectory of BMI and the time-varying effect of network exposure to friends with overweight/obesity while controlling for demographic covariates. Results: Hispanic students had a significantly higher initial BMI compared with non-Hispanic students (p < 0.01). There was a significant positive slope for time on BMI growth (p < 0.01). Greater personal network exposure to friends with overweight/obesity was associated with a significant 0.65-point average increase in BMI (p < 0.05) at the first follow-up time point (T2) and a significant 0.62-point average increase in BMI (p < 0.01) at the last follow-up (T4) while controlling for covariates. Conclusions: Using structural equation modeling to understand the relationship between BMI and social networks, we found that increased network exposure to peers with overweight/obesity is associated with higher individual BMI, demonstrating that friendships may influence adolescents' weight status over time.

Sport Participation Associations With Child Friend Selection and Physical Activity While at Summer Care Programs

Child physical activity (PA) declines during summer reducing PA-related health benefits. Summer care programs (e.g., Boys & Girls Clubs) can promote active play while providing opportunities for friendships. Sport participation is a positive influence on PA and social development. Purpose: This article investigates the role of sport participation in PA attainment, perceived skill competency, and social connection at a summer care program. Methods: Children self-reported PA, sport participation, and the names of up to five peers whom they played with most at the program at the start (T1; n = 100; M age = 9.94 years; SD = 1.34; 47% male) and end (T2; n = 77; M age = 9.83 years; SD = 1.46; 51% male) of summer. Network autocorrelation models were used to determine if child sport participation was significantly associated with those they played with at the program. Results:Children who reported sport participation reported significantly more PA than those who did not at T1, but not T2. Child sport participation was significantly related to that of the peers they said they spent time with while at the program for T1 (β = 0.07, p < .01), but not T2 (β = 0.06, p = .10). Additionally, PA (β = 0.08, p < .01; β = 0.07, p = .01) and skill competency (β = 0.11, p = .02; β = 0.15, p < .01) were significantly associated with sport participation at both time points. While sports participation was a key factor in child friendships at the start of summer, the program allowed children, regardless of sport participation, to become friends outside of sports. Conclusions: These results suggest summer care programs promote PA through play and provide opportunities for children to facilitate friendships regardless of sport participation.

Examining food intake similarities in adolescent best friend dyads using longitudinal Actor-Partner Interdependence Models

Little is known about how adolescent best friends may affect each other's food intake. This study explored whether friendship selection and socialization mechanisms explained potential food intake similarities in adolescent reciprocated best friend dyads. We also tested whether socialization processes were moderated by dyad member's relative zBMI. Members of 145 same-gender best friendship dyads (56% female; Mage = 12.79; SDage = 0.61) reported on their intake of food obtained from home and from outside the home at the beginning and the end of the school year through food frequency questionnaires. Longitudinal Actor-Partner Interdependence Models results showed no indication of selection or socialization, and very limited evidence for the moderation of socialization processes by relative zBMI. These findings indicate that focusing on adolescent reciprocated best friends in dietary interventions may not be valuable.

I Play, You Play, We Play: Concurrent Activity at Play Streets

Purpose: Despite multiple health benefits, many children and teens do not achieve recommended amounts of physical activity (PA). Temporary changes to the built environment like Play Streets, temporarily closing streets to create safe places to play, are one solution to encourage PA in summer months. Play Streets can promote social cohesion by creating opportunities for concurrent activity, being active in the same area simultaneously. This study assesses concurrent activity at Chicago PlayStreets. Methods: During summer 2018, the System for Observing Play and Recreation in Communities (SOPARC) and iSOPARC mobile application were used to measure PA at PlayStreets (n = 11) organized by eight community partners. Odds ratios were used to determine odds of observing an individual as active when in the same target area as another individual, and when in the same target area as an active individual, separated by sex and age categories. Results: Presence of an active individual significantly increased odds of observing an individual as active for several sex and age stratifications. Specifically, presence of active children or an active male adult significantly increased odds of observing children and teens as active. In contrast, presence of another person alone was not shown to significantly increase odds of observing an individual as active, except in two instances when stratified by sex and age. Conclusions: Active male adults have a significant positive impact on activity levels at PlayStreets underlining the importance of engaged male figures. Additionally, findings suggest that active children can promote PA among other children at PlayStreets.

Summer Friends and Physical Activity: Social Network Effects on Child Self-Reported Physical Activity at Summer Care Programs

Summer is a time of reduced physical activity (PA) for children; however, summer care programs (SCPs) can provide opportunities for children to be active and foster friendships. This study investigated associations between PA and friendship formation at SCPs. Children (ages 8-12 years) from two SCPs reported demographics, PA, and up to five friends at the program. Exponential random graph modeling determined significant factors associated with connections at each time point and between time points. PA was a significant factor in sending and maintaining friendship connections. A further understanding of the social dynamics which assist in the maintenance of PA behaviors during summer may improve the odds children engage in the recommended amounts of PA during this crucial time.

Service, Activism, and Friendships in High School: A Longitudinal Social Network Analysis of Peer Influence and Critical Beliefs

Scholars acknowledge that friends shape youth civic engagement, but the relative contribution of peer influence and critical beliefs to civic behaviors has yet to be disaggregated. Informed by sociopolitical development and critical consciousness theories, the present study used longitudinal social network analysis to examine peer socialization and adolescents' awareness of systemic inequities in relation to participation in service and activist activities at a high school serving primarily low-income Latinx youth. Students were surveyed in May 2019 and May 2020 (N = 354; 51% female; in 2019, Mage = 15.9, age range 14.4 to 18.5). The results yielded evidence of peer influence on service activities, but not activism or perceptions of inequities. In contrast, adolescents' perception of inequities predicted their activist behavior, but not service, after controlling for network effects and individual covariates. The school provided scaffolding for service activities, but not activist activities, potentially explaining the salience of service participation in youth friendship networks.

High school students’ friendship network, physical activity and residential locations – a stochastic actor based model

Evidence shows that adolescents do not do enough physical activity (PA), which could contribute to childhood overweight and obesity. Studies have shown that both the built environment and social networks could influence adolescents’ PA, but more studies are needed to investigate their combined influence using longitudinal data. We used a stochastic actor-based model analyzing two waves of Add Health data to test if (1) home location has a significant influence on high school student’s friendships, and (2) the neighborhood built environment has a significant influence on high school student’s PA while controlling for friendship networks. The results indicate that students’ PA level emulated peers’ PA levels and students who lived closer together, increased the likelihood of forming friendships. However, the built environment variables that described adolescents’ residential neighborhoods did not show a significant influence on students’ PA dynamics. This study contributes to our understanding of the joint impacts of social networks and home location on adolescents’ friend networks and PA dynamics in urban settings.

Toward understanding the functions of peer influence: A summary and synthesis of recent empirical research

Compelling evidence demonstrates that peer influence is a pervasive force during adolescence, one that shapes adaptive and maladaptive attitudes and behaviors. This literature review focuses on factors that make adolescence a period of special vulnerability to peer influence. Herein, we advance the Influence-Compatibility Model, which integrates converging views about early adolescence as a period of increased conformity with evidence that peer influence functions to increase affiliate similarity. Together, these developmental forces smooth the establishment of friendships and integration into the peer group, promote interpersonal and intragroup compatibility, and eliminate differences that might result in social exclusion.

Personal Social Networks and Adiposity in Adolescents: A Feasibility Study

Background and Objective: Weight-related behaviors are determined by multiple individual and contextual factors, with recent evidence implicating personal social networks (PSNs). Greater understanding of these relationships could help inform healthy weight promoting interventions. We conducted a feasibility study among youth at risk of obesity to document process outcomes, to discern relationships between PSN features and weight-related behaviors, and to generate hypotheses with respect to perceived social support (SS) and sex. Methods: Participants (egos) nominated up to 10 people (alters) with whom they discussed important matters. Egos reported their own and each alter's age, sex, body shape, lifestyle behaviors, relation, frequency of exercising with each alter, and of being encouraged by each alter to exercise. We examined relationships between PSN features and weight-related outcomes and explored the role of SS, using both correlational and linear regression analyses. Results: There were 45 participants (mean age 16.4 years) and body mass index z-score (zBMI) ranged from -1.2 to 3.9. There were few missing responses to PSN items; broad variation across most items, including SS scores, was reported. Correlations pointed to plausible relationships implicating PSN features and lifestyle behaviors. In exploratory analyses, network-based SS was positively associated with adiposity in girls and negatively associated in boys, while lifestyle role modelling was not associated with adiposity. Conclusions: Our findings support the feasibility of measuring the PSN in youth and the potential for using social network analysis to investigate social and behavioral mechanisms associated with obesity.

Agent-Based Models for Assessing Complex Statistical Models: An Example Evaluating Selection and Social Influence Estimates from SIENA

Although agent-based models (ABMs) have been increasingly accepted in social sciences as a valid tool to formalize theory, propose mechanisms able to recreate regularities, and guide empirical research, we are not aware of any research using ABMs to assess the robustness of our statistical methods. We argue that ABMs can be extremely helpful to assess models when the phenomena under study are complex. As an example, we create an ABM to evaluate the estimation of selection and influence effects by SIENA, a stochastic actor-oriented model proposed by Tom A. B. Snijders and colleagues. It is a prominent network analysis method that has gained popularity during the last 10 years and been applied to estimate selection and influence for a broad range of behaviors and traits such as substance use, delinquency, violence, health, and educational attainment. However, we know little about the conditions for which this method is reliable or the particular biases it might have. The results from our analysis show that selection and influence are estimated by SIENA asymmetrically and that, with very simple assumptions, we can generate data where selection estimates are highly sensitive to misspecification, suggesting caution when interpreting SIENA analyses.

Peer network studies and interventions in adolescence

Peer influence occurs across a wide variety of behavioral domains, which is an important reason for peer-led interventions: interventions in which peers are involved in the delivery of the program. These programs are promising in combatting undesirable behaviors (e.g. risk behavior) and promoting desirable behavior (e.g. healthy lifestyle), but it was shown recently that the effectiveness of these programs is modest at best and the mechanisms underlying programs' effectiveness are poorly understood. Research is needed that promotes understanding of the relative, cumulative, and interactive impacts of different types of peer relations and unpacks the various mechanisms underlying peer selection and influence. This has the potential to yield insights that advance theory and optimize peer-led interventions.

Correlations between Physical Activity Participation and the Environment in Children and Adolescents: A Systematic Review and Meta-Analysis Using Ecological Frameworks

Physical activity (PA) and sports are efficient ways to promote the young generation’s physical and mental health and development. This study expected to demonstrate the complexity of correlates associated with children’s and adolescents’ non-organized PA participation. Following the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols (PRISMA), a systematic review and meta-analysis were applied. Seven electronic databases were systematically searched to identify eligible articles based on a series of inclusion and exclusion criteria. The internal validity of the systematic reviews thus identified was evaluated using a validated quality instrument. Calculations were produced in SPSS 27.0 and Comprehensive Meta-Analysis 3.3. Thirty-nine eligible studies (N = 324,953) with moderate to high quality were included. No potential publication bias was detected using statistical analyses. The meta-analysis revealed that the overall ecological factors correlated positively with children and adolescents’ PA; the meta-analytic average of the correlations was (′r = 0.32, p < 0.001). Results from subgroup analysis indicated that theory-based influence factors achieved moderate effect with boys (′r = 0.37, p < 0.001) and girls (′r = 0.32, p < 0.001) in PA participation. Interestingly, higher correlations were found between ecological factors and twins’ PA participation (′r = 0.61, p = 0.001). Further, individual (′r = 0.32, p < 0.001), macro-, and chronosystems factors (′r = 0.50, p < 0.001) appeared slightly more influential than microsystems factors (′r = 0.28, p < 0.001) on children and adolescents’ PA participation. Although findings from the included studies covered were to some extent heterogeneous, it is possible to identify consistent correlates of PA in children and adolescents. The results supported that PA is a complex and multi-dimensional behavior, which is determined by numerous biological, psychological, sociocultural, and environmental factors. Future studies that focus on the integration effect of macrosystem and chronosystem environmental factors, and apply longitudinal designs and objective measurements are encouraged to further unfold the complexity of the ecological system and its implications in promoting children and adolescents’ PA participation.

Built environment in programs to promote physical activity among Latino children and youth living in the United States and in Latin America

To prevent obesity among Latino youth in the United States and Latin America, it is necessary to understand the specific context and interplay of physical activity (PA) and the built environment (BE). This paper aims to advance the research agenda of BE and PA for obesity prevention in Latin America and among Latino youth in the United States by (1) identifying environmental indicators to inform the design of interventions and policy, (2) identifying interdisciplinary methodological approaches for the study of the complex association between BE and PA, and (3) presenting case studies of PA-promoting BE programs. A group of U.S. and Latin American scientists collaboratively worked to propose innovative indicators of the BE, methodological approaches for the study of the complex association between BE and PA, and review case studies of PA-promoting BE programs in both regions. The results identified gaps in knowledge, proposed environmental indicators (e.g., landscape, street design, mobility patterns, and crime and safety), reviewed methodological approaches (social network analysis, citizen science methods), and case studies illustrating PA-promoting BE programs (i.e., play streets, active school transport, and school setting interventions). The obesity prevention among Latino and Latin American youth requires advanced research on BE and PA addressing context-specific priorities and exchanging lessons learned.

The school policy, social, and physical environment and change in adolescent physical activity: An exploratory analysis using the LASSO

PURPOSE

We examined the association between the school policy, social and physical environment and change in adolescent physical activity (PA) and explored how sex and socioeconomic status modified potential associations.

METHODS

Data from the GoActive study were used for these analyses. Participants were adolescents (n = 1765, mean age±SD 13.2±0.4y) from the East of England, UK. Change in longitudinal accelerometer assessed moderate-to-vigorous physical activity (MVPA) was the outcome. School policy, social and physical environment features (n = 267) were exposures. The least absolute shrinkage and selection operator variable selection method (LASSO) was used to determine exposures most relevant to the outcome. Exposures selected by the LASSO were added to a multiple linear regression model with estimates of change in min/day of MVPA per 1-unit change in each exposure reported. Post-hoc analyses, exploring associations between change in variables selected by the LASSO and change in MVPA, were undertaken to further explain findings.

FINDINGS

No school policy or physical environment features were selected by the LASSO as predictors of change in MVPA. The LASSO selected two school social environment variables (participants asking a friend to do physical activity; friend asking a participant to do physical activity) as potential predictors of change in MVPA but no significant associations were found in subsequent linear regression models for all participants (β [95%CI] -1.01 [-2.73;0.71] and 0.65 [-2.17;0.87] min/day respectively). In the post-hoc analyses, for every unit increase in change in participants asking a friend to do PA and change in a friend asking participants to do PA, an increase in MVPA of 2.78 (1.55;4.02) and 1.80 (0.48;3.11) min/day was predicted respectively.

CONCLUSIONS

The school social environment is associated with PA during adolescence. Further exploration of how friendships during adolescence may be leveraged to support effective PA promotion in schools is warranted.

Odds of Meeting Cancer Prevention Behavior Recommendations by Health Information Seeking Behavior: a Cross-Sectional HINTS Analysis

People who seek health information frequently may be more likely to meet health behavior goals; however, people use many different information sources. The purpose of this paper is to assess how different sources of health information influence likelihood of meeting cancer prevention behavior guidelines. Logistic regression of cross-sectional data from 6 years of the Health Information National Trends Survey (HINTS) was conducted. Independent variables included first source of health information, gender, age, race, education level, income, cancer history, general health, and data year; dependent variables were fruit and vegetable intake, exercise, smoking, mammography, Pap test, and colon cancer screening. Those who seek health information from doctors, the internet, or publications had higher odds of meeting more cancer prevention guidelines than those who do not seek health information. Those who used healthcare providers as an initial information source had higher odds of meeting diet, cervical, and colon cancer screening recommendations, while using the internet as an initial source of health information was associated with higher odds of meeting diet, smoking, and colon cancer screening recommendations. No health information source was associated with meeting either exercise or mammography recommendations. People should be encouraged to seek health information to help them meet their behavior goals, especially from sources that are more likely to be accurate and encourage cancer prevention behavior. Future research is needed to understand the accuracy of health information and what kinds of health information have positive influences on cancer prevention behavior.

Social support from family and friends for physical activity in adolescence: analysis with structural equation modeling

Social support is an important predictor for the maintenance of physical activity in adolescence. Thus, the social-ecological approach values the impact of individuals or groups interaction with available resources in the social environment for adopting an active lifestyle. This study analyzes social support from family and friends for adolescents to practice physical activity. Guided by the Social-Ecological Theory, an observational cross-sectional structural equations modeling was applied to 2,710 Brazilians adolescents aged from 14 to 18 years. We identified that the greater the social support from friends (β = 0.30; RMSEA = 0.065; CFI = 0.953; TLI = 0.922; SRMR = 0.048) and family, the greater the adolescents physical activity (β = 0.27; RMSEA = 0.015; CFI = 0.997; TLI = 0.995; SRMR = 0.013). However, support from both sources indicated no adequate adjustment values in the same study model. Our findings suggest that adolescents who perceive social support from family members or friends practice more physical activity, confirming that social support is important for physical activity promotion.

First-year college students' weight change is influenced by their randomly assigned roommates' BMI

BACKGROUND

There is ongoing debate about whether friends' greater similarity in Body Mass Index (BMI) than non-friends is due to friend selection, shared environments, or peer influence.

METHODS

First-year college students (n = 104) from a southwestern U.S. university were randomly assigned roommates during the university's housing process, effectively removing friend selection effects. Participant BMI was measured up to four times (T1-T4) across 2015-2016. The influence of roommate baseline BMI (T1) on change in participant BMI over time (T2-T4) was analyzed using a linear mixed effects model adjusted for individual socio-demographics, linear time trends, baseline BMI, and physical clustering of students. A sensitivity analysis examining floormates was also conducted.

RESULTS

Consistent with roommate influence, participants randomized to roommates with a higher BMI gained more weight between times T2 and T4 (β = 0.06; 95% CI = 0.02, 0.10). No shared environment effects (shared campus or floor) were found.

CONCLUSIONS

Randomly assigned roommates influenced each other's weight trajectories. This clarifies that BMI convergence can occur outside of friend selection or shared environments mechanisms.

Network Effects on Adolescents' Perceived Barriers to Physical Activity

BACKGROUND

Adolescent physical activity (PA) is widely linked to positive health outcomes. Unfortunately, 80% of adolescents do not meet recommendations, which may be due to perceived barriers to PA. Peer interactions significantly affect adolescent PA behaviors. This study aims to analyze distribution of PA barriers throughout adolescent friendship networks and barriers' associations with PA.

METHODS

Adolescents (N = 383, mean = 10.77 y, SD = 1.30 y, 51.4% male) reported frequency of experiencing PA barriers (body related, social, fitness, convenience, and resource) and names of their friends. Average steps and minutes of moderate- to vigorous-intensity PA per day were measured using accelerometers. Linear network autocorrelation models determined if friends perceived barriers similarly when compared with nonfriends and analyzed relationships between barriers and objective PA measures while controlling for network effects.

RESULTS

Moderate- to vigorous-intensity PA, steps per day, body-related barriers, and social barriers displayed significant network effects, suggesting significant association with the scores of their friends. Average steps per day were significantly associated with age, sex, and social barriers, while inversely associated with fitness barriers.

CONCLUSIONS

This research suggests adolescents' perceived PA barriers are significantly associated with those of their friends. Researchers and practitioners aiming to reduce barriers to PA among adolescents may wish to assess peer reinforcing effects.

Effects of a Physical Activity Program Potentiated with ICTs on the Formation and Dissolution of Friendship Networks of Children in a Middle-Income Country

This paper assesses the potential cohesion effect of a physical activity (PA) school-based intervention potentiated using text messages (SMS) through analyzing longitudinally the friendship network structure and the mechanisms of the formation and dissolution of friendships. Three schools (n = 125 participants) in Bogotá, Colombia, were randomly assigned into three groups: Modulo Activo Recreo Activo (MARA) + SMS (networks 1 and 2), MARA (networks 3 and 4), and control (no intervention: networks 5–7). We collected socio-economic, health-related, network structure, and intervention satisfaction variables in the baseline and after 10 weeks on July–November 2013. For each classroom network, we conducted four models using a temporal and static network approach to assess (1) temporal social network changes, (2) friendship homophily, (3) friendship formation and dissolution mechanisms, and (4) effect of SMS on the networks’ cohesion. We found that (1) social cohesion emerged in the four intervened networks that were measured over time with transitivity and homophily driven by clustering, (2) the intervention affected the mechanisms of friendship formation and dissolution, and (3) MARA + SMS on average created more social cohesion and 3.8 more friendships than the program alone. Potentially, school-based interventions with information and communication technologies (ICT) such as MARA + SMS could encourage social cohesion among children. The particular characteristics of each school network need to be considered when developing school-based interventions.

Examining the Role of Weight Status and Individual Attributes on Adolescent Social Relations

PURPOSE

Weight stigmatization during adolescence may compromise the development of social relations important for the development. This study examined the associations between weight status and likelihood of nomination (indegree) for five different social network types-friendship, romantic, admiration, succeed, and popularity.

METHODS

Data for the study were from 1,110 tenth grade students (aged 11-19 years) from four high schools in one Los Angeles school district in 2010. Multiple Poisson regression analyses using generalized linear model were conducted to examine the relationship between weight status (underweight/normal weight/overweight measured with body mass index calculated from self-reported height and weight) and adolescents' indegree for the five different networks.

RESULTS

Obese adolescents were significantly less likely to be nominated as romantic interest (odds ratio [OR]: .29, 95% confidence interval [CI]: .19-42), admired (OR: .80, 95% CI: .65-.97), or popular (OR: .71, 95% CI: .57-.88) compared with their normal weight peers. Overweight adolescents were also less likely to be nominated as a romantic interest (OR: .57, 95% CI: .42-.78) or popular (OR: .67, 95% CI: .53-.84) compared with those who were normal weight. Underweight adolescents were also less likely to be nominated as friends (OR: .76, 95% CI: .60-98), someone admired (OR: .61, 95% CI: .42-.89), likely to succeed (OR: .62, 95% CI: .44-.87), or popular (OR: .40, 95% CI: .25-.64).

CONCLUSIONS

Our results suggest weight status is associated with being selected by peers into different types of adolescent networks. Underweight, overweight, and obese adolescents are at an increased risk for social isolation because of their weight. This may have a negative impact on their peer relations important for social development, self-esteem, and mental health.

Are Feminine Body Weight Norms Different for Black Students or in Black Schools? Girls' Weight-Related Peer Acceptance across Racialized School Contexts

Adolescent girls with overweight or obesity are less socially integrated than their thinner peers. We examine racial-ethnic differences in girls' weight-related friendship patterns, especially noting Black-white distinctions given their different norms about the ideal feminine form. We also test whether schools with more Black students see diminished weight-related differences in peer integration for all girls and/or for Black girls. Using 1994-1995 data from the National Longitudinal Study of Adolescent to Adult Health, we predict the number of friendship nominations girls receive conditional on their weight status, race-ethnicity, and school's racial composition. Both white and Black girls with overweight or obesity are less integrated than their thinner peers regardless of the school's Black enrollment rate. Hispanic girls with overweight are more integrated than white girls with overweight, particularly in schools with low Black enrollments. The relative consistency of girls' weight-related friendship patterns demonstrates the ubiquity of dominant feminine thinness norms.

Neither influence nor selection: Examining co-evolution of political orientation and social networks in the NetSense and NetHealth studies

Political orientation is one of the most important and consequential individual attributes studied by social scientists. Yet, we know relatively little about the temporal evolution of political orientation, especially at periods in the life course during which individuals are forming new social relationships and transitioning to new relational contexts. Here we use Stochastic Actor-Oriented models (SAOMs) to examine the co-evolution of political orientation and social networks using two feature-rich, temporal network datasets from samples of students making the transition to college at the University of Notre Dame (i.e. the NetSense and NetHealth studies). Overall, we find a great deal of stability in political orientation, with a slight tendency for the 2011 NetSense study participants to become more conservative during their first four semesters in college, but not the 2015 NetHealth study participants. Partisanship is the best predictor of changes in political orientation, with students who identify or vote as Republicans becoming more conservative over time. Neither network influence nor selection processes seem to be driving observed changes. During this formative period, relatively stable identities such as party affiliation predict changes in political orientation independently of local network dynamics, selection processes, socio-demographic traits, and dispositional factors.

Young adults' BMI and changes in romantic relationship status during the first semester of college

Purpose

Identify how higher Body Mass Index (BMI) and weight discrimination are associated with romantic relationship formation and termination in young adults, and if the association was consistent for males and females.

Methods

First-year students (N = 1096) at entry to university (Time 1) provided BMI and self-reports of weight discrimination and romantic relationship status (in a relationship vs single); 550 were successfully resampled four months later (Time 2). Logistic generalized estimating equations (GEEs) examined if Time 1 relationship status was predicted by BMI and weight discrimination. Logistic GEEs were used to determine if Time 1 BMI and weight discrimination predicted Time 2 relationship status for the strata of students in, and out, of a relationship at Time 1.

Results

At baseline, students were less likely to be in a relationship if they had a higher BMI (OR = 0.94, 95% CI = 0.92, 0.96) or reported weight discrimination (OR = 0.69, 95% CI = 0.53, 0.90). When stratified by gender, the association between higher BMI and weight discrimination with relationship status was only observed for females. Longitudinally, a BMI-based selection effect was observed for romantic relationship formation, but not termination. Of the students who were single at Time 1, each one unit higher baseline BMI decreased the odds of the student transitioning to a relationship by 9% at Time 2 (OR = 0.91, 95% CI = 0.85, 0.96). When stratified by gender the association of higher BMI decreased odds of relationship formation was only significant for females. No weight discrimination differences for selection in or out of a romantic relationship were observed.

Conclusions

These findings suggest a weight-related selection effect for romantic relationship initiation, but not termination, in young female adults with lower BMIs. Weight discrimination was not associated with romantic relationship initiation or termination in this sample.

Social Influences on Obesity: Current Knowledge, Emerging Methods, and Directions for Future Research and Practice

PURPOSE OF REVIEW

Individuals tend to be socially connected with those of similar weight and obesity status. To inform future research and intervention development, we reviewed recent literature examining social influences on weight with a focus on mechanisms of social influence, populations studied, and emerging analytical methods.

RECENT FINDINGS

Social networks appear to influence weight gain and weight loss. It remains unclear what underlying mechanisms (e.g., social norms, social comparison, behavioral modeling) drive this relationship. Stochastic actor-oriented modeling is an important method in the field, but other work has leveraged natural experiment or randomized designs to study social influence. Future networks and obesity research should examine social influence mechanisms, focus on diverse populations across the life course, and carefully consider how to adequately control for competing factors of social selection and physical environments.

Timing of puberty in boys and girls: Implications for population health

Puberty is marked by substantial increases and emerging sex differences in psychological disorders and risky behaviors. However, few studies have examined these effects beyond adolescence, and the previous literature has been dominated by samples of White girls. The current study examines the broadest known set of health sequelae related to traditional pubertal markers and peer-relative pubertal timing in a representative sample of 14,545 U.S. youth from the National Longitudinal Study of Adolescent to Adult Health.

Maturational timing was assessed by age at menarche for girls and physical development for boys (e.g., facial hair, voice change), and then categorized as early (1 SD below mean), on-time, or late (1 SD above mean) within-sex. Early and late peer-relative timing was assessed by a self-report of looking “much older” or “much younger” than one's peers. We examined psychological (depressive symptoms, antisocial behavior), behavioral (number of sex partners, drug use, physical activity, screen time, sleep hours), and physical health (self-reported health, BMI) outcomes during adolescence and young adulthood in a series of sex-stratified regression analyses using survey weights and a comprehensive set of sociodemographic covariates.

Results indicated that, overall, earlier pubertal timing (i.e., maturational timing and peer-relative timing) put both girls and boys at risk during adolescence, while later timing was protective. However, longitudinal models revealed mixed results. For instance, early maturational timing was associated with higher young adult BMI (girls: β = 0.139, p < .01; boys: β = 0.107, p < .01), but later timing for boys was associated with both risky (e.g., more screen time; β = 0.125, p < .05) and health promoting (e.g., more sleep; β = .296, p < .01) behaviors. Analysis of this holistic set of outcomes with sex differences in mind allows for more careful evidence-based recommendations for adolescent health promotion.

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Early or late puberty predicts health, but there is little longitudinal research.

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Perceived pubertal development relative to peers also predicts health outcomes.

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Links between pubertal timing and long-term health were more pervasive for girls.

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Adolescent psychological symptoms and health behaviors explain long-term links.

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Results point to the need for high-quality puberty education early in life.

Social Network Analysis in Child and Adolescent Physical Activity Research: A Systematic Literature Review

BACKGROUND

Regular physical activity (PA) has many benefits for children and adolescents, yet many do not meet PA recommendations. Social context is important for promoting or discouraging PA among children and adolescents. This review aimed to identify social network variables related to PA among children and adolescents.

METHODS

A systematic review of the literature was conducted in September 2018 using PsycINFO, MEDLINE, PubMed, and Web of Science. Included articles needed to (1) be focused on children (aged 5-11 y) or adolescents (aged 12-17 y), (2) include a measure of PA, (3) include a measure of egocentric or sociocentric social connection in which alters were nominated, and (4) perform an analysis between network data and PA.

RESULTS

A search of 11,824 articles was refined to a final sample of 29 articles. Social network themes and concepts such as homophily, centrality, and network composition were related to child and adolescent PA behavior across the literature.

CONCLUSIONS

The impact of an individual's social network is evident on their PA behaviors. More research is needed to examine why these networks form in relation to PA and how interventions can utilize social network analysis to more effectively promote PA, especially in underserved and minority populations.

Peer social network processes and adolescent health behaviors: A systematic review

Research has highlighted the importance of peers for determining health behaviors in adolescents, yet these behaviors have typically been investigated in isolation. We need to understand common network processes operating across health behaviors collectively, in order to discern how social network processes impact health behaviors. Thus, this systematic review of studies investigated adolescent peer social networks and health behaviors. A search of six databases (CINAHL, Education Resources Information Centre, Embase, International Bibliography of the Social Sciences, Medline and PsycINFO) identified 55 eligible studies. The mean age of the participants was 15.1 years (range 13-18; 51.1% female). Study samples ranged from 143 to 20,745 participants. Studies investigated drinking (31%), smoking (22%), both drinking and smoking (13%) substance use (18%), physical activity (9%) and diet or weight management (7%). Study design was largely longitudinal (n = 41, 73%) and cross-sectional (n = 14, 25%). All studies were set in school and all but one study focused on school-based friendship networks. The Newcastle-Ottawa Scale was used to assess risk of bias: studies were assessed as good (51%), fair (16%) or poor (33%). The synthesis of results revolved around two network behavior patterns: 1) health behavior similarity within a social network, driven by homophilic social selection and/or social influence, and 2) popularity: health behavior engagement in relation to changes in social status; or network popularity predicting health behaviors. Adolescents in denser networks had statistically significant lower levels of harmful behavior (n = 2/2, 100%). Findings suggest that social network processes are important factors in adolescent health behaviors.

The association of weight status and weight perception with number of confidants in adolescents

Weight status and self-weight perception are related to social relationship issues. Studies have suggested links between non-normal weight status or weight perception and youths having fewer confidants, but these relationships are unclear and remain to be studied. This preliminary cross-sectional study examined the effects of weight status and weight perception on the number of confidants in adolescents. Self-report data from 15,279 grade 7–12 students (54.2% boys) were analyzed. The number of confidants (0–3 or ≥ 4) was examined, according to five weight status categories (underweight, low-normal weight, mid-normal weight (reference), high-normal weight, overweight, with Body Mass Index corresponding to ≤ 18.5, ≤ 20.0, ≤ 22.5, ≤ 25.0 and > 25.0 in adults, respectively), and five weight perception categories (too thin, a bit thin, good (reference), a bit fat, too fat). Boys and girls who were overweight and those who perceived themselves to be too fat were significantly more likely to have few confidants. High-normal weight in girls and self-perception of being a bit fat in boys were also associated with having few confidants. In boys, underweight and self-perception of being too thin were additionally associated with having few confidants. Adolescents with non-normal weight status or weight perception may have fewer confidants and require more social support.

The Interplay of Adolescents' Aggression and Victimization with Friendship and Antipathy Networks within an Educational Prosocial Intervention

How the interplay between peer relationships and behaviors unfolds and how this differs between classrooms is an understudied topic. This study examined whether adolescents befriend or dislike peers whom they consider as aggressor or victim and whether these results differ in classrooms that received an intervention to promote prosocial behavior compared to classrooms without the intervention. The sample was composed of 659 seventh graders (Mage = 12.32; 48% girls) from nine intervention and seven control classrooms in eight schools in Santiago, Chile. It was hypothesized that adolescents in intervention classrooms would be less befriended and more disliked by classmates who considered them as aggressors, and more befriended and less disliked by classmates who considered them as victims, compared to control classrooms. Longitudinal multiplex social network analyses (RSiena) indicate that antipathies toward peers considered as aggressive and victimized were significantly lower in intervention classrooms than in control classrooms, but no significant differences were found for friendships. These findings suggest that the impact of an educational intervention may go beyond changing individual behavior and extend to the way peer relations develop in classrooms.

Do income inequalities in higher weight status depend on social integration?

Those with higher incomes tend to have better health outcomes, including healthy weight status. We use data from the 2003-2008 National Health and Nutrition Examination Survey (NHANES) to examine whether the association between higher weight status and social integration varies by income. We examine gender differences in weight status, measured by BMI and obesity, by social integration and income, and find evidence that high social integration is a risk factor for higher weight status among low-income men. The association between income and higher weight status operates differently for women and men and is dependent, in part, on their level of social integration. Income is negatively associated with weight status for men who are highly integrated, but is positively associated with weight status among men who have low integration. We conclude that higher numbers of close friends and family places low-income men at greater risk of higher weight status.

Do Birds of a Feather Flock Together Within a Team-Based Physical Activity Intervention? A Social Network Analysis

BACKGROUND

Homophily is the tendency to associate with friends similar to ourselves. This study explored the effects of homophily on team formation in a physical activity challenge in which "captains" signed up their Facebook friends to form teams.

METHODS

This study assessed whether participants (n = 430) were more similar to their teammates than to nonteammates with regard to age, sex, education level, body mass index, self-reported and objectively measured physical activity, and negative emotional states; and whether captains were more similar to their own teammates than to nonteammates. Variability indices were calculated for each team, and a hypothetical variability index, representing that which would result from randomly assembled teams, was also calculated.

RESULTS

Within-team variability was less than that for random teams for all outcomes except education level and depression, with differences (SDs) ranging from +0.15 (self-reported physical activity) to +0.47 (age) (P < .001 to P = .001). Captains were similar to their teammates except in regard to age, with captains being 2.6 years younger (P = .003).

CONCLUSIONS

Results support hypotheses that self-selected teams are likely to contain individuals with similar characteristics, highlighting potential to leverage team-based health interventions to target specific populations by instructing individuals with risk characteristics to form teams to help change behavior.

Personal Network Characteristics as Predictors of Change in Obesity Risk Behaviors in Early Adolescence

The potential for peers to influence obesity risk behavior increases in adolescence, yet there are knowledge gaps of how behaviors are modified in response to peers over time. This study examined how personal friendship network characteristics were associated with obesity-related behaviors from late childhood to early adolescence. Two waves of friendship, physical activity, screen time, and dietary recall data were collected from 11- to 13-year-old students (99% retention) in Australia (n = 308) over a five- to eight-month period. Regression models identified friendship network characteristics that predicted later health behaviors which varied by gender and behavior type, such as the number of friends positively associated with physical activity intensity (males) and screen time (females). The need for considering context to influence behavior change is discussed.

Evaluating Potential Behavioral Mediators for Increasing Similarity in Friends' Body Size among College Students

College students and their friends become more similar in weight status over time. However, it is unclear which mediators explain this relationship. Using validated survey measures of diet, physical activity, alcohol intake, sleep behaviors, mental health, and food security status, we take a comprehensive look at possible factors associated with excess weight gain that may explain friends’ convergence on body mass index (BMI), waist circumference, waist to hip ratio, and waist to height ratio over time. We use linear mixed models applied to a longitudinal dataset of first-year college students to examine whether these variables satisfy two criteria for potential candidate mediators of friends’ influence on anthropometrics—cross-sectional similarity among friends (n = 509) and longitudinal associations with increasing anthropometrics (n = 428). While friends were similar on some survey measures (such as dining hall use, home cooked meal consumption, fruit intake, alcohol intake, hours of sleep, and stress). Only dining hall use and stress emerged as potential explanations for why friends’ BMI and anthropometric change may be similar. Given that only a few variables satisfied the two criteria as potential mediators, future research may need to consider alternative measurement approaches, including real-time assessments, objective measurements, and alternative factors causing the convergence of friends’ and college students’ body size over time.

Classroom ability composition and the role of academic performance and school misconduct in the formation of academic and friendship networks

This paper examined the association between friendship and academic networks and how the connections these networks have with academic performance and school misconduct differ when comparing three types of classrooms where students were grouped based on their academic ability (i.e., high-, low-, and mixed-ability). The sample was composed of 528 seventh to ninth graders (M_age = 15; 64.1% girls) from 12 classrooms (four in each category of ability grouping) across two waves in five schools in Chile. The effects of academic performance and school misconduct on receiving academic and friendship nominations were examined, as well as the interplay between academic and friendship relationships. Furthermore, the extent to which similarity in adolescents' academic performance and school misconduct contributed to the formation and maintenance of academic and friendship relationships was examined. Sex, socioeconomic status, and structural network features were also taken into account. Longitudinal social network analyses (RSiena) indicated that (1) in high-ability classrooms students chose high-achieving peers as academic partners; (2) in high-ability classrooms students avoided deviant peers (i.e., those high in school misconduct) as academic partners; and (3) academic relationships led to friendships, and vice versa, in both high- and low-ability classrooms. Whereas the interplay of friendship and academic relationships was similar in high- and low-ability classrooms, the formation and maintenance of academic networks unfolded differently in these two types of classrooms.

Friendship as a social mechanism influencing body mass index (BMI) among emerging adults

Background

Social relationships have been proposed as a significant factor shaping obesity risk. The first year of college, a period of major social, behavioral, and weight changes, provides a context well-suited to tracking longitudinally the impact of shifting friendships on weight outcomes. This study sought to identify social mechanisms impacting BMI change among emerging adults.

Methods

An analytic sample of 276 college students (71.0% female, 52.2% non-White) provided repeated reports of relationships and BMI was measured up to four times during 2015–2016. Stochastic actor-oriented models were used to examine change in BMI through social influence and change in friendships over time, controlling for sex and race/ethnicity.

Results

At baseline, mean BMI was 24.2±4.5 kg/m². Overall, mean BMI increased over time; individual decreases in BMI were uncommon. There was a selection effect of BMI: participants with BMIs between 22 and 26 kg/m² were most likely to be nominated as a friend. While participants did not select friends based on BMI similarity, participants who were reported as friends were more likely to experience convergence in BMI over time relative to the BMIs of non-friends (p = 0.015). An increase in BMI (versus stability or a decrease) was more likely for those whose friends had a higher BMI on average compared to participants whose friends had the same or lower BMI (OR = 2.85, 95% CI = 1.22, 6.71).

Conclusion

Analyses indicated BMI affected friend selection, not through students selecting friends with similar BMI, but rather, by students avoiding friends with more extreme BMI levels.

Diet and Physical Activity of Korean Female Adolescents in Their Peer Networks

PURPOSE

The purpose of this study was to examine and compare the diet and physical activity behaviors of female adolescents and their friends within classroom-based peer networks in Korea.

DESIGN

Complete social network analysis was used to examine the influence of classroom-based peers on adolescents' diets and physical activity. Data were collected by self-report from 99 female adolescents in three classrooms.

METHODS

Diet and physical activity behaviors were measured using the Adolescent Food Habit Checklist, food frequency questions, and the International Physical Activity Questionnaire. Female adolescents were asked to nominate close friends within their classroom. Descriptive statistics for diet and physical activity were generated; social network data were analyzed using social network analysis.

FINDINGS

Most participants were normal-weight, 18-year-old adolescents. Across three classrooms, adolescents' dietary behaviors were connected with those of their classroom-based peer networks; however, similar outcomes were not identified for physical activity.

CONCLUSIONS

Clusters of diet behaviors for Korean female adolescents were identified in classroom-based peer networks. Developing interventions based on these shared behaviors could be effective in improving these behaviors. Additional studies should explore potential barriers to physical activity for Korean female adolescents and their classroom-based peers.

CLINICAL RELEVANCE

The current study found that Korean female adolescents' dietary behaviors were associated with their peers'. Healthcare providers should consider involving peers when developing interventions to improve the diet of Korean female adolescents.

Physical Activity Among Israeli-Arab Adolescent Males: How Do Parenting Styles Matter?

Physical activity contains many benefits for adolescents' physical and mental health, and also for building healthy living routines and habits for the future. The current study examined the associations between parenting styles and adolescents' physical activity among Israeli-Arab families of male adolescents, in seeking to boost the limited information on this most important topic. Participants consisted of 177 male Israeli-Arab adolescents ( M = 13.93, SD = 1.42) with normal weight. Controlling for the participants' age, weight, and grades in school, parenting styles explained about 30% of the variance in the participants' reports of their physical activity, with the authoritative and authoritarian parenting inversely correlated with the latter variable. Adolescents who perceived their parents as authoritative were reportedly more physically active than their counterparts who perceived their parents as authoritarian. In common with previous studies, the findings suggest that authoritative parenting may be a cross-culturally preferable style in fostering a desired physical activity rate among adolescents.

The rippling dynamics of valenced messages in naturalistic youth chat

Even though human behavior is largely driven by real-time feedback from others, this social complexity is underrepresented in psychological theory, largely because it is so difficult to isolate. In this work, we performed a quasi-experimental analysis of hundreds of millions of chat room messages between young people. This allowed us to reconstruct how-and on what timeline-the valence of one message affects the valence of subsequent messages by others. For the highly emotionally valenced chat messages that we focused on, we found that these messages elicited a general increase of 0.1 to 0.4 messages per minute. This influence started 2 s after the original message and continued out to 60 s. Expanding our focus to include feedback loops-the way a speaker's chat comes back to affect him or her-we found that the stimulating effects of these same chat events started rippling back from others 8 s after the original message, to cause an increase in the speaker's chat that persisted for up to 8 min. This feedback accounted for at least 1% of the bulk of chat. Additionally, a message's valence affects its dynamics, with negative events feeding back more slowly and continuing to affect the speaker longer. By reconstructing the second-by-second dynamics of many psychosocial processes in aggregate, we captured the timescales at which they collectively ripple through a social system to drive system-level outcomes.

Social exclusion of the adolescent with overweight: study of sociocentric social networks in the classroom

BACKGROUND

Multiple studies have shown the social consequences of suffering overweight, with social exclusion or isolation as some of the most important. In order to study the social patterns among adolescents, we have set as objectives to analyse the position of the individual within their network from a sociocentric perspective, comparing the relational pattern of the adolescents suffering from overweight with those who are normal weight.

METHOD

This was a cross-sectional descriptive study using logistic regression and social network analysis. We analysed the contact patterns of 235 adolescents in 11 social networks, classifying contact into three levels of intensity: minimum, intermediate and maximum (friendship). The WHO reference was used for the variable of overweight.

RESULTS

The prevalence of overweight was 30.2% (25.5% overweight and 4.7% obesity). An analysis of the relational patterns of individuals with overweight showed that at the minimum contact level, they established fewer relationships and less closeness (odds ratio [OR]: 2.32; confidence interval [CI] 95%: 1.17-4.66; p-value: 0.016). This effect was more marked in female adolescents. At intermediate contact level, they had few relationships and low prestige (OR: 3.29; CI: 95%; 1.03-10.51; p-value: 0.045, OR: 3.18; CI: 95%; 1.00-10.04; p-value: 0.049, respectively). At maximum contact level (friendship), female adolescents related little with other adolescents (OR: 3.78; CI: 95%; 1.07-13.32; p-value: 0.038).

CONCLUSIONS

Adolescents with overweight take up peripheral positions within their social network, choosing by themselves not to establish contact with others. Social network analysis is crucial to detect adolescents with overweight at risk of exclusion and help alleviate psychological and social deficits.

Development of Friendship and Task Values in a New School: Friend Selection for the Arts and Physical Education but Socialization for Academic Subjects

Friends provide important social contexts for student development. Research has shown that adolescent friends are similar to each other in their interest and values for different school subjects. Yet our current understanding does not extend to knowing whether selection, deselection, or socialization processes are responsible for this phenomena. Without this knowledge, it is very difficult for parents, teachers, and schools to know how and when to intervene. This study investigated selection, deselection, and socialization effects on adolescent students' task values for academic (languages, math and science, and social sciences) and non-academic subject areas (the arts and physical education). A social network approach was used to examine two waves of annual data collected from school-based networks of adolescents in the first and second years of high school education in Finland (N = 1419; female = 48.6%; mean age at first measurement point = 16). The results revealed that adolescents tended to select friends with similar levels of task values (friend selection) for the arts and physical education, but friends did not become more similar in these areas over time (friend socialization). In contrast, there was evidence of friend socialization, but not friend selection, for the academic school subjects. Across all subjects, differences in task values did not predict friendship dissolution (friend deselection). These findings suggest that to a significant extent, students make agentic choices in developing friendship with schoolmates based on their task values in non-academic subjects. The resultant friend contexts that individuals created, in turn, affected their task values in academic subject areas. These results shed light on the complexity of friend effect mechanisms on task values at the subject domain-specific level.

Applications of social network analysis to obesity: a systematic review

People's health behaviours and outcomes can be profoundly shaped by the social networks they are embedded in. Based on graph theory, social network analysis is a research framework for the study of social interactions and the structure of these interactions among social actors. A literature search was conducted in PubMed and Web of Science for articles published until August 2017 that applied social network analysis to examine obesity and social networks. Eight studies (three cross-sectional and five longitudinal) conducted in the US (n = 6) and Australia (n = 2) were identified. Seven focused on adolescents' and one on adults' friendship networks. They examined structural features of these networks that were associated with obesity, including degree distribution, popularity, modularity maximization and K-clique percolation. All three cross-sectional studies that used exponential random graph models found individuals with similar body weight status and/or weight-related behaviour were more likely to share a network tie than individuals with dissimilar traits. Three longitudinal studies using stochastic actor-based models found friendship network characteristics influenced change in individuals' body weight status and/or weight-related behaviour over time. Future research should focus on diverse populations and types of social networks and identifying the mechanisms by which social networks influence obesity to inform network-based interventions.

Social network body size is associated with body size norms of South Asian adults

Aims

To examine the association between social network body size and body size norms in South Asian adults.

Methods

Participants (n = 766) from the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study (2014-2018) provided detailed information about their five closest network members. Participants' perceptions of their network members' body sizes, their own body size (self-body size), and a healthy body size for men and women (body size norms) were assessed using the Stunkard 9-figure scale. Adjusted hierarchical linear regression models were used to examine associations between the average body size of network members and perceived body size norms.

Results

Participants' average age was 59.1 years (SD = 9.2) and 44.1% were women. Participants reported an average network body size of 4.0 (SD = 1.1). The average body size norm for male and female Stunkard images was 3.6 (SD = 1.0) and 3.4 (SD = 0.8), respectively. Social network body size was positively associated with increasing body size norms (β-coefficient = 0.31, 95% CI: 0.26, 0.36), independent of self-body size.

Discussion

Social networks may influence body size norms in South Asian adults. Long-term follow up of the MASALA cohort will determine if social network body size and body size norms are associated with weight- control behaviors and weight change.