The prevalence of overweight among children has tripled in the last 40 years. Although recent data suggest that childhood overweight rates have begun to plateau, 32% of youth aged 2 to 19 years are overweight or at risk of becoming overweight (1,2). Furthermore, childhood overweight contributes to type 2 diabetes, adult obesity, and heart disease, along with impaired self-esteem and depression (3).

Adolescent overweight is largely a product of familial obesity risk (4), but environmental influences can augment the expression of overweight in children with a family history of obesity, continuing into adulthood. A social network approach to research and intervention design accounts for social contexts such as family, schools, neighborhoods, or communities, revealing how people are interconnected and influence one another. A social network approach is a relational perspective that frames research involving individuals and their families and communities, in addition to the methodologic tools that are used in social network analysis. We discuss the use of a social network approach in interventions for adolescent overweight by considering 1) recent developments in the science of obesity genetics, 2) the importance of social context, 3) communal coping as a mechanism for behavior change within social networks, and 4) specific recommendations for using social networks to prevent overweight.

A recent study estimates that more than 70% of adiposity in 10-year-olds is due to genetic factors, and approximately 20% is due to socioenvironmental contributions (4). Genome-wide association studies have located common genetic variants associated with fat mass, weight, and susceptibility to obesity. Several genes isolated through these studies, including FTO (5) and MC4R (6), may eventually help scientists to explain the global scale of the obesity epidemic and the biological mechanism for the heritability of obesity in families.

Other research has identified factors associated with the behavioral transmission of obesity risk from parents to their children (7). Eating disinhibition, susceptibility to hunger, and eating in the absence of hunger all appear to be biologically heritable traits. Thus, a child's family health history, along with shared behaviors and familial environments, must be considered in efforts to prevent and treat obesity (8).

Excessive caloric intake and a lack of physical activity are 2 major environmental causes of adolescent overweight. Both structural and behavioral environments in which adolescent social networks operate are inextricably linked to their eating behaviors and physical activity levels.

Early childhood feeding practices are usually established in the home and often translate into eating patterns during adolescence. Variations in food preferences and portions among preschool children are associated with the extent to which parents introduce new foods and encourage healthful eating habits (9). Moreover, maternal feeding practices appear to influence the dietary patterns of girls, suggesting that the relational significance of parental influence on their children may be sex-specific (10).

Likewise, early childhood activity levels translate into similar patterns of physical activity during adulthood (11). Physical activity among adolescents is a social behavior, which is partly dependent on neighborhoods and recreational spaces. Built environments can limit or facilitate levels of adolescent physical activity. Playgrounds that are accessible via sidewalks and safe intersections have been associated with higher levels of physical activity among youth (12).

Mutual friendship ties, not merely biological family or relationships found within the household, can contribute to an adult's risk of obesity (13), but little is known about whether the social mechanisms associated with weight gain in adults pertain to adolescents. Studies of adolescent social networks have identified the extent to which clique formation, the tendency for people to form social ties with others who are similar (14), are associated with weight status and physical activity. One study found that adolescent friendships tended to cluster on the basis of weight status (15). The boys who were friends engaged in similar levels of physical activity; however, this finding was not noted within girl friendship networks (16). Another study found similarities in the consumption of sweet foods and fast foods and types of physical activities among male friends, and female friends were similar in the time spent on computer-based leisure activities (17).

The mechanisms of social influence on adolescent overweight vary, but all depend on social interaction. Parents can serve as role models, especially for younger children whose health behaviors are completely influenced by their parents' habits (18), and older children may look to their friends, teachers, and community leaders as role models for their own health behaviors (19). Indirect processes can occur through cultural or group norms and attitudes. For example, adolescents' attitudes about body image can be influenced by social and cultural norms (20).

A social network approach fits within a socioecological model for obesity interventions, because social networks form and operate within the social contexts that influence health behaviors and behavior change (21). Capitalizing on these interpersonal relationships may enhance the effectiveness of health promotion interventions (22).

Communal coping is a process in which interpersonal relationships are the conduit to behavior change among multiple members within a particular social network, such as families (23). Its use in obesity prevention is novel, because it prioritizes relational over individual processes. From a communal coping perspective, individuals define themselves in terms of their interconnectedness and relationships with their family, friends, neighbors, and community. Thus, when faced with a shared health problem, a cooperative approach to address the problem that involves family and friends may be particularly effective (23).

Health interventions that use communal coping can target 3 interpersonal pathways (Figure 1): 1) communication about a health problem, such as shared risk factors, 2) shared appraisals of the problem, and 3) development of cooperative strategies to reduce negative impact (23). Interventions can focus on educating family members about collective risk due to shared family history, environment, and behaviors, and promoting increased communication about family risk of overweight and associated diseases. Similar efforts can motivate communication about shared risk factors among friends in neighborhoods and communities, leading to shared appraisals among those who are socially connected. The success of communal coping depends on cooperative support mechanisms. Support can be directed at emotion-focused coping to address, for example, low self-esteem or psychological impacts of stigma associated with overweight and obesity. Cooperative support also can be geared toward problem-focused coping by addressing dietary behavior and physical activity.

Obesity prevention must account for the complexity of overweight, including a child's familial risk of obesity and social relationships. Most previous interventions have focused on a single social sphere, such as household or school. Furthermore, family-oriented interventions often engage an affected child and a single caregiver, rather than considering the complex social environment that might surround children and their families. An intervention that focuses on the family system will have limited success without consideration of the social influences on both parents' and children's behaviors outside of the family context. Similarly, a school-based intervention that does not consider the familial social environment or interpersonal influences within the neighborhood or community settings would also be limited.

Thus, we recommend that interventions focus on 3 settings simultaneously (Figure 2, Table): R1 and R2) the household and the child's family outside of the household; R3) the neighborhood and community, to engage the parents' social network and social influences on the child outside of the school setting; and R4) the school, to engage the child's social network.

According to Barabasi, "Growing interest in interconnectedness has brought into focus an often ignored issue: networks pervade all aspects of human health" (28). Network perspectives will continue to advance the study of childhood and adolescent overweight. We suggest a new and stronger focus on the potential to garner interpersonal processes to address the obesity problem. Consideration of family and social networks may contribute to sustainable behavior change and improve the effectiveness of prevention and treatment interventions. Although challenging, curbing the obesity epidemic will undoubtedly depend on the coordinated efforts of many agencies and institutions to support culturally sensitive programs that consider both family and peer interactions.