Objective: Outpatient treatment in restricted eating disorder: indirect calorimetry during dynamic monitoring. Design: A retrospective observational study. Subjects: Twenty seven women affected by restricted eating disorder (essentially anorexia nervosa) with a body mass index [weight (kg)/height (m2)] of 17.29±2.47 were studied. The sample was compared as itself control during rehabilitative way. Interventions: Fat mass (FM) and fat free mass (FFM) were determined by anthropometry technique. REE/day and respiratory quotient (RQ,VCO2/VO2) were measured by indirect calorimetry using a Calorimeter Vmax 29n-Sensor Medics-California. Skinfold thickness and circumferences were also measured. Arm muscle area (AMA) and fat area were calculated by formulas reported in Frisancho. Results: The data indicated a positive correlation between AMA, VO2/ml/min and resting energy expenditure (REE)/day values examined during follow-up of patients. The increase of these parameters indicated a good monitoring index correlated to a FFM recovery during psychonutritional rehabilitation. Conclusion: Indirect calorimetry represents a useful approach for determining REE and prescribing diets in these patients. Moreover, the combined use of anthropometric techniques allows to accurately assess and adjust therapy according to the patient’s progress. This study shows that restricted eating disorders are characterized by a recovery of FFM related to improvement of body weight and REE/day. On the contrary, the increase of AFA revealed a recovery of fat-metabolism (corresponding to RQ decrease) and lipid/carbohydrates oxidation improvement, only in the presence, at the same time, of O2 consumption increase.