Junk Food Intake in Adolescents: Processes and Mechanisms Driving Consumption Similarities Among Friends

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Adolescents Junk Food Intake Junk Food Intake in Adolescents: Processes and Mechanisms Driving Consumption Similarities Among Friends Kayla de la Haye, RAND Corporation Garry Robins, University of

1 Adolescents Junk Food Intake Junk Food Intake in Adolescents: Processes and Mechanisms Driving Consumption Similarities Among Friends Kayla de la Haye, RAND Corporation Garry Robins, University of Melbourne Phil Mohr, CSIRO Food & Nutritional Sciences Carlene Wilson, Flinders University/Cancer Council South Australia Young peoples consumption of low-nutrient, energy-dense (LNED foods) junk foods has increased in recent decades Reduced diet quality and increased caloric intake via empty calories (Jahns, 2001) Implications for health outcomes, e.g., obesity, diabetes Consumption of LNED food typically occurs out of the home (Briefel, 2009) SRA Biennial Meeting, March Environments Influencing LNED Food Intake How do out-of-home environments influence LNED food intake in young people? Junk food consumption often in school/peer settings Peer contexts shape many adolescent health behaviors, particularly social behaviors Social influence on eating strongest for close ties (de Castro, 1994) Friends consume similar amounts of LNED food Friends alike in their intake of snack foods (Feunekes, 1998) Male friends alike in their intake of high-calorie foods (de la Haye, 2010) Social Influence on Eating Situational food norms & social modeling Lab-based studies show consistent effects of food matching in adults and children (e.g., Conger et al, 1980; Herman et al., 2003) We eat more when our eating companions eat more (and less when they eat less) Matching norm evident for strangers, but stronger for close relationships E.g., Adolescents tend to match the food intake of friends more than unfamiliar peers (Salvy, 2009) Research Questions & Aims Are adolescents influenced by their friends junk food consumption in naturalistic settings? Does food matching occur out of the lab? Does this explain observed dietary similarities among friends? Aim 1: Examine if adolescents intake of LNED foods is influenced by the intake of their friends does socialization in friendships account for similarities? controlling for similarities that may arise through friendship choices. Research Questions & Aims Aim 2: Examine mechanisms that underpin socialization of LNED food intake among friends Why do friends emulate each other? Imitation/automatic response to food cues ( mindless eating ) Social-cognitive mechanisms: social environment influences behavior via perceptions of social norms or other related beliefs Do cognitive mechanisms mediate the influence of friends intake on adolescent intake?

Study Sample & Procedure Co-evolution of adolescent friendship networks and LNED food intake using stochastic actor-based (SAB) models (Snijders et al.

6 years School 2: N = 156, 55% male, Mage = 13.

2 Study Sample & Procedure Co-evolution of adolescent friendship networks and LNED food intake using stochastic actor-based (SAB) models (Snijders et al., 2010) Sample Two grade 8 cohorts of Australian adolescents (90% response) N = 378, nested in two schools (2 friendship networks) School 1: N = 222, 53% male; Mage = 13.6 years School 2: N = 156, 55% male, Mage = 13.7 years Procedure Opt-out parental consent Panel data collected at 3 time points over the school year Self-report paper questionnaires completed at school Measures Friendships Students nominated their best friends in their school grade LNED food intake over the previous month FFQ: Frequency of consumption for 14 items (e.g. ice cream, chocolate, soda, fast foods, french fries, etc.) on 7pt. scale Mean of 14 items (α =.80 to.86) Attitudes & cognitions regarding consumption of LNED foods Intentions, attitudes, peer norms, control, self-efficacy Control attributes Gender, ethnicity, weekly pocket money, home group class, overweight, perceived parent LNED food intake Junk Food Descriptive Statistics Mean intake for averaged food items from Wave 1 to Wave 3 Junk Food Descriptive Statistics Variation in intake of specific food items at Wave 1 (School 1) Network Descriptive Statistics School 1 Friendship Network Characteristics of the friendship networks: Wave 1 to Wave 3 Wave 1 Wave 2 Wave 3

Obesity in Social Networks School 2 Friendship Network Wave 1 Wave 2 Statistical Analysis: Behavior Model Stochastic actor-based models for the co-evolution of networks and behavior (Snijders,

3 Obesity in Social Networks School 2 Friendship Network Wave 1 Wave 2 Statistical Analysis: Behavior Model Stochastic actor-based models for the co-evolution of networks and behavior (Snijders, Steglich, & Schweinberger, 2007) RSiena version 4.0 Wave 3 Results: Behavior Model Results: Behavior Model LNED food intake predicted friendship choices: School 1: intake and popularity No evidence that friendships formed among peers with similar intake Friendship choices also based on: Similarities in gender, ethnicity (S1), and pocket money (S1) Sharing the same home group class Structural effects: reciprocating friendships, forming ties with friends of friends Was adolescent LNED food intake influenced by their friends? Yes, in both schools Intake was explained by: Friends intake Pocket money (S2) Overall decline (S1) Summary Adolescent intake of LNED foods was influenced by their friends Over the school year, adolescents emulated the LNED food intake levels of their close friends Distribution of high LNED food consumers in the friendship network over time (School 1) An overall decline in LNED food intake in School 1 Not explained by observed variables But, adolescents with high consuming friends were likely to adopt or maintain high levels of consumption

4 Mediation Model: Mechanisms of Influence Aim 2: Test if friends influence on adolescent LNED food intake was mediated by cognitive mechanisms Did friends intake of LNED foods predict adolescent attitudes and cognitions about LNED foods? Did this explain (fully or partially) similarities in behavior (influence of friend intake on adolescent intake)? Mediation model Stochastic actor-based model Simultaneous co-evolution of friendships, LNED food intake, and attitudes/cognitions about LNED food intake Intentions, attitudes, peer norms, control, self-efficacy Part A: Effect of friends LNED food intake on adolescent cognitions and attitudes towards LNED foods No significant effects Friends intake of LNED foods did not predict changes in adolescent cognitions or attitudes Part B: Effect of adolescent cognitions and attitudes towards LNED foods, on their own intake do cognitions influence behavior? Part C: Effect of adolescent LNED food intake, on their cognitions and attitudes towards LNED foods does behavior influence cognitions? No evidence that friends influence on LNED food intake was mediated by cognitive mechanisms Adolescent cognitions or attitudes towards LNED food intake was not predicted by their friends intake Additionally, there was little evidence that individuals attitudes/cognitions predicted subsequent behavior Rather, LNED food intake predicted intentions, attitudes, and norms Self perception theory: we come to know our beliefs through observing our behavior (Bem, 1972) Conclusions Adolescents LNED food intake was influenced by their friends intake Participants were likely to adopt eating behaviors that were similar to the behaviors of their friends Consistent with matching effects found in the lab Influence explains friend similarities in observational studies Findings did not support social cognition models (e.g. Ajzen, 1991) Influence process was not mediated via cognitive mechanisms Imitation/automatic socialization process? Mindless eating? Implicit (vs. explicit) cognitive process? Individual beliefs and demographics did not predict intake Environmental factors peer intake and possibly an unmeasured broader environmental factor explained change Implications Findings support claims that external social and environmental cues impact junk food intake in young people Friends may be especially salient behavior models Particularly for LNED foods, that are often eaten out of home Interventions and policies limiting exposure to LNED foods in peer contexts may be effective in reducing consumption Limiting these social cues may also have a positive effect on adolescent intentions to consume these foods, and beleifs Mechanisms that underpin the clustering of health outcomes (e.g., obesity): possible points for intervention

5 Thank you Co-authors Garry Robins, University of Melbourne Phil Mohr, CSIRO Food & Nutritional Sciences Carlene Wilson, Flinders University & Cancer Council Contact Kayla de la Haye RAND Corporation

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