This paper examines how the intensity of social media use affects anti-fat attitudes by considering the mediating effects of three main attributions—internal, social, and physical—on obesity stigma. Participants were 213 college students in the United States who completed a paper survey. A mediation analysis model using the PROCESS macro (Model 4) was employed to test the research question and hypotheses. Intensity of social media use did not show a relationship with internal and social causes, but it did show a significant relationship with physical causes. Physical causes had a negative mediating effect on anti-fat attitudes. This implies that the higher the intensity of social media use, the higher the physical causes and the lower the anti-fat attitudes. The intensity of social media use had no direct relationship with anti-fat attitudes. Theoretical and practical implications were suggested.