Abstract
OBJECTIVE: Social media (SM) is a source of appearance-focused content that promotes idealized bodies and appearances. It also spreads misinformation about nutrition and fitness practices. While SM use has been linked to attitudes toward eating disorders, its association with orthorexia nervosa and muscle dysmorphia-characterized by obsessive behaviors around diet and body image-remains underexplored. This study systematically reviewed quantitative research on the relationship between SM use and symptoms of orthorexia nervosa and muscle dysmorphia. METHOD: The review was registered on PROSPERO and adhered to PRISMA guidelines. Twenty-two studies (orthorexia nervosa: n = 17; muscle dysmorphia: n = 5) were included, primarily cross-sectional and conducted on non-clinical populations. Study quality was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. RESULTS: Most studies found that higher SM use was associated with greater orthorexia nervosa and muscle dysmorphia symptoms, with specific contents -such as posts regarding nutrition, thinness, and exercise- particularly associated with orthorexia nervosa. Platforms like Instagram, Tumblr, and Grindr demonstrated stronger associations with orthorexia nervosa symptoms. Gender differences were also observed. CONCLUSIONS: Findings suggest a link between SM use and orthorexia nervosa symptoms, with preliminary evidence also supporting an association with muscle dysmorphia symptoms. Future research should explore causality and develop targeted prevention and treatment strategies to mitigate these risks.