Situated within research on youth, participatory politics, and media framing of obesity, this study examined how undergraduate students in a media literacy course engaged with obesity discourse as a nexus of civic participation. Twenty-nine students enrolled on the course identified frames of obesity in plus-size model Tess Holliday's Instagram posts surrounding her controversial Cosmopolitan cover in 2018. Analysis of these frames -- self-validation, injustice of fat-shaming and stigmatization, influences of Instagram celebrities on fat embodiment, and health stereotypes of obese people -- enabled the students to critique activist responses to accepted body norms and moral values facilitating weight bias. In efforts to reframe obesity within their social media communities, the students created and shared online media content, prioritizing societal influences in obesity representation. In this process, students cultivated participatory practices of comprehending and sharing (social) media framings of bodies and health. Hence, this article offers contextualized understandings in youth digital engagement learning.