Objective The aim of this review is to analyse the studies about cost and clinical implications that malnutrition causes in the Spanish hospitals. Material and methods The review of the literature was carried out through a bibliographic search in Web of Science following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria and analyse the cost of treatment of malnourished and anorexia nervosa (AN) patients Results Seventeen studies with economic data related to malnutrition were included. The employment of a nutritional screening is the first tool to determinate the prevalence. Malnutrition is related to an incremental cost due to a longer hospital stay, expensive treatment, and higher rate of readmissions. Malnourished patients present more clinical complications, more infections, and higher mortality. No studies were found with economic data of AN in Spain. Conclusions The prevalence of malnutrition is over 20%, with the elderly patients being the most affected. Nutritional screening is not implanted in all Spanish hospitals in spite of its proven cost-effectiveness. The cost and the clinical implications of malnutrition make this disease a health national problem. The knowledge of the real cost of AN treatment would increase the interest of public institutions on the development of specific Nutritional Screening tools for an early detection of AN.