Social media amplifies beauty standards that shape adolescent body image and weight-related behaviors. This study investigates the role of aesthetic capital in perceived body-related social success and weight-loss behaviors among Spanish adolescents, with a focus on the mediating effect of social media pressure. Using a mixed-methods approach, we integrate survey data from 1,082 adolescents (12–17 years old) with qualitative insights from fitness microinfluencers and health care professionals. Quantitative findings indicate that adolescents associate toned bodies with greater social advantages, and perceived social media pressure significantly predicts engagement in weight-control actions. Interviews with microinfluencers reveal the tension between content monetization and the reinforcement of idealized body standards, while health care professionals highlight the psychological toll of aesthetic comparison, linking it to anxiety, body dissatisfaction, and extreme dietary practices. These findings suggest that aesthetic capital functions as a mechanism of social success and exclusion in digital spaces, reinforcing hierarchies of desirability and status.