A Mixed Methods Evaluation of Social Support and Homophily in Weight Loss


The prevalence of obesity within the US continues to rise, and many individuals elect to involve supportive others in their weight loss. Social support is generally helpful in weight management, but its mechanisms are less understood. One construct that deserves further attention is homophily, or the notion that “birds of a feather flock together.” This dissertation examined the role of homophily in social support and weight loss within 2 behavioral weight loss interventions. The first study utilized data from Opt-IN, a 6-month behavioral weight loss study that examined the influence of assigning a participant’s weight loss “Buddy” to formal support training, and analyzed the moderating relationship of homophily variables (race, ethnicity, and age) between Buddy training assignment and participant weight loss outcomes. Results revealed that the magnitude of difference between participant and Buddy ages increased the effectiveness of Buddy training assignment on participant weight loss. The second study was a qualitative interview study in which former Opt-IN study participants discussed their experience of receiving social support from their Buddy before, during, and after Opt-IN. Participants tended to select Buddies with whom they were already close, but endorsed the presence of social support “mismatches” during the intervention that left room for improvement. The final study was a secondary analysis of weight loss study groups within ENGAGED, a behavioral weight loss study; specifically, the study sought to investigate the role of homophily variables (i.e., race, ethnicity, age, sex, gender, and BMI) within weight loss groups, and the impact of homophily on weight loss within groups. Results suggest homophily may explain variance in weight loss among study groups, but the study was not adequately powered to detect statistical difference. While the generalizability of these studies is limited given the lack of racial and ethnic diversity, results nonetheless suggest the important role of homophily in social support, and by extension, weight management more broadly.  

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