Social networks and social norms are associated with obesity treatment outcomes

Objective To examine whether overweight social network members and normative influence for obesity are associated with weight loss outcomes during obesity treatment. Methods Participants (N = 214) in a behavioral weight loss trial reported (a) the weight status of various members of their social network and (b) the level of obesogenic normative influence within their social network. Weight was objectively assessed before and after treatment. Results At baseline, participants with partners and best friends who were overweight and those with more children and relatives who were overweight had higher BMIs (P's < 0.03). However, social norms for obesity were not associated with baseline BMI. During treatment, participants lost an average of 4.4% of initial body weight, and social influence factors were adversely associated with weight loss outcomes. Having more casual friends who were overweight at baseline and being part of a social network with stronger social norms for unhealthy eating predicted poorer weight losses (P's < 0.023). Remaining social influence factors and changes in social influence were not associated with treatment outcomes. Conclusions Whereas weight status may "cluster" in social networks, only weight status of casual friends and normative influence for unhealthy eating were associated with obesity treatment outcomes.