Background <p>Restrained eating has often been studied from either sociocultural or attachment perspectives, but relatively few studies have examined how attachment-related factors may operate alongside sociocultural influences. Additionally, most studies have focused on Western populations, despite evidence suggesting that sociocultural influences on eating behaviors vary across cultures. Guided by both sociocultural and attachment theories, the present study examined how passive social media use and peer attachment security were related to restrained eating among Chinese college women, and whether thin-ideal internalization and body satisfaction mediated these associations.</p> Methods <p>Data were collected from 404 Chinese college women aged 18–30 through Wenjuanxing, a widely used online survey platform in China. Participants completed the Chinese version of the Surveillance Use Scale, the Ideal-Body Internalization Scale, the Body Image State Scale, and the Inventory of Parent and Peer Attachment.</p> Results <p>A moderated mediation model revealed that passive social media use, peer attachment security, and their interaction were significantly associated with restrained eating, with different mediating mechanisms. First, passive social media use was directly associated with restrained eating. Second, peer attachment security was indirectly associated with restrained eating through body satisfaction. Importantly, the interactive effect of passive social media use and attachment was directly associated with restrained eating. Specifically, this effect was significant only for individuals with low levels of peer attachment security.</p> Conclusions <p>By integrating selected sociocultural pathways and attachment perspectives within a non-Western context, this study offers a nuanced understanding of restrained eating among Chinese college women. Findings suggest that passive social media use and peer attachment security function through distinct mechanisms. Moreover, the effect of passive social media use is contingent on peer attachment security, suggesting that interpersonal resources may buffer vulnerability to digital environmental pressures.</p> <p><?noindent??>The findings highlight the importance of considering both digital experiences and interpersonal relationships when examining eating-related behaviors. Practically, interventions may benefit from promoting awareness of passive social media use while also fostering supportive peer relationships and positive body image.</p>