Societal body ideals are shifting from thinness for women and muscularity for men to a unified “fit ideal” that emphasizes both leanness and muscle mass across genders. This study tested a revised tripartite influence model, and employed the Fit-Ideal Internalizatfion Test, in a sample of 288 Australian adults (Mage = 22.7; 31% men). Path analysis examined links among social media pressure, fit-ideal internalization, appearance comparison, body dissatisfaction, compulsive exercise, and muscularity-oriented eating (e.g., ingestion of high levels of protein). Results showed that fit-ideal internalization directly predicted compulsive exercise and muscularity-oriented eating in both men and women and mediated the influence of social media pressure on these behaviors. In women only, both internalization and appearance comparison mediated the link between social media pressure and body dissatisfaction, and body dissatisfaction and peer pressure directly predicted muscularity-oriented eating. Although men and women internalized the fit ideal to a similar degree, their behavioral outcomes differed, indicating gender-specific pathways. These findings highlight the importance of gender-informed, media-literate interventions. Clinicians and educators should tailor strategies to the distinct social pressures identified, while recognizing overlap. Public health campaigns and policies must promote inclusive messaging that disrupts the progression from fit-ideal internalization to body dissatisfaction, disordered eating, and compulsive exercise across genders.