Among the restrictive eating and eating disorders, anorexia nervosa (AN) and atypical anorexia nervosa (AAN) are the ones that present the greatest medical complications. Objective: Describe the characteristics of patients with AN and AAN and their differences in demographic and clinical para-meters. Patients and Method: The records of patients <19 years of age with AN admitted to Clinica Santa María between 2013 and 2019 were reviewed. The evolution time, amenorrhea, z-BMI, percentage and speed of weight loss, and complications were recorded. Results were expressed as mean and standard deviation or median and range. Comparisons were made using the Mann-Whitney test, the t-student test, and the chi-square test; Pearson’s coefficient was used for correlations. Results: 76 patients with AN were admitted (64% AAN). The median age was 15.4 years. AN and AAN differed in age at diagnosis (p < 0.03), z-BMI (p < 0.001), bradycardia (p < 0.009), blood pressure (p < 0.003), and cholesterol (p < 0.02), without other differences. The z-BMI correlated with heart rate (r = 0.39 p < 0.002); systolic pressure (r = 0.43 p<0.000), and HDL (r =-0.39 p < 0.005). The percentage of weight loss was correlated with time of amenorrhea (r = 0.27 p < 0.05); alanine aminotransferase (r = 0.0.37 p < 0.031), and HDL (r = 0.47 p < 0.001) and the speed of weight loss with glycemia (r =-0.46 p < 0.001) and urea nitrogen (r =-0.39 p < 0.005). Conclusion: AAN was the most frequent AN condition in this sample and variables such as the percentage and speed of weight loss were as important as BMI in medical complications.