Friends and social contexts as unshared environments: A discordant sibling analysis of obesity- and health-related behaviors in young adolescents

Authors: SALVY, SARAH-JEANNE - University Of Southern California; FEDA, DENISE - University Of Buffalo; EPSTEIN, LEONARD - University Of Buffalo; Roemmich, James

Submitted to: International Journal of Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2016
Publication Date: 12/20/2016
Publication URL: https://handle.nal.usda.gov/10113/5695410
Citation: Salvy, S., Feda, D.M., Epstein, L.H., Roemmich, J.N. 2016. Friends and social contexts as unshared environments: A discordant sibling analysis of obesity- and health-related behaviors in young adolescents. International Journal of Obesity. doi:10.1038/ijo.2016.213.

Interpretive Summary: Social influences such as being alone or with peers and friends may affect adolescents’ weight control behaviors that influence whether they stay at a healthy weight or become obese. Scientists at the Grand Forks Human Nutrition Research Center found that the adiposity of the best friend was associated with the adiposity of the targeted adolescent such that heavier adolescents are more likely to have a heavier best friend. If the adolescent’s best friend was heavier it was also more likely that the targeted adolescent would drink more soda and spend more time in sedentary behaviors like watching television. Adolescents who spent more time with friends were more active and less sedentary. This work helps to understand how social influences during adolescence can change their eating and activity habits. Peers and friends can help or hinder adolescents' weight control behaviors.

Technical Abstract: Objective. This study uses a weight-discordant sibling design to examine the relationships between best friend’s body mass index z-score (zBMI) and siblings’ zBMI and obesity-related health behaviors (energy intake, consumption of sugar-sweetened beverages [SSB], physical activity and sedentary time). Methods. Siblings and their best friends’ height and weight were measured using a digital scale and stadiometer. Multi-pass dietary recalls were used to assess energy intake and SSB consumption. Siblings’ physical activity was measured using seven days of accelerometry and sedentary behaviors/screen time was assessed using experience sampling methodology (EMS)/ecological momentary assessment (EMA). EMS/EMA was also used to assess the number of occasions participants spent alone and in the presence of friends. Multilevel models (family as random effect) were used to estimate the relationships between best friends’ zBMI and time spent alone or with friends and siblings’ zBMI and obesity-related health behaviors. Results. Best friend’s zBMI significantly predicted sibling’s zBMI, even when controlling for child’s birth weight. Best friend’s zBMI was also positively associated with siblings’ soda consumption and time engaged in sedentary behaviors. Number of occurrences being active with friends was positively associated with siblings’ overall physical activity, whereas number of occurrences alone was negatively associated with accelerometer counts regardless of siblings’ adiposity. Conclusion. A friends’ zBMI and the social context are unshared environmental factors associated with variability in adiposity among biologically-related weight-discordant siblings.