Introduction: Studies investigating the occurrence of osteoporosis in Eating Disorders (EDs) are limited. This thesis investigates the extent to which individuals with different ED diagnoses and ED behaviours suffer from bone loss, and studies bone loss in both adolescents and adults with EDs. Finally, this thesis will investigate the current treatments to improve bone health in EDs, and make recommendations for both treatment and future research avenues. Methods: Chapters 5 and 8 of this thesis present systematic reviews of the literature, firstly investigating Bone Mineral Density (BMD) across ED sub-types using a meta-analysis (Chapter 5), and secondly investigating current treatment options and the mechanisms behind these treatments (Chapter 8). Chapters 6 and 7 investigate bone health outcomes in a general population sample, the Avon Longitudinal Study of Parents and Children. Lifetime ED behaviours and ED diagnoses are investigated in adults as predictors of BMD (Chapter 6), and ED behaviours are investigated as longitudinal predictors of BMD and fracture occurrence in adolescents (Chapter 7). Finally, the mechanisms associated with bone loss are reviewed and treatment options are discussed (Chapter 8). Results: Chapter 5 found that not only Anorexia Nervosa (AN), but also Bulimia Nervosa (BN) was associated with low bone mineral density (BMD). Chapter 6 advanced upon this and found individual ED behaviours (fasting and restricting) to be predictive low BMD in adult women. Chapter 7 found that fasting, purging and excessively exercising in adolescence were longitudinal predictors of fracture occurrence up to early adulthood. Finally, Chapter 8 found that bisphosphonate therapy, and also transdermal oestrogen were the only empirically supported treatments to improve BMD in AN. Conclusions: The results from this thesis advance on the current literature as we find that not only AN, but also BN and individual ED behaviours are all predictive of poor bone health outcomes in both adults and adolescents. Treatment options are severely limited for this group, and those available have an uncertain safety profile. Future research should aim to protect bone health in all EDs, and develop safe and efficacious treatments.