Restricting-type of anorexia nervosa (AN-R) is a serious disorder affecting adolescents and young adults, and decreases quality of life over long period. Successful weight restoration is an important prognostic factor for disease outcome; however, the underlying mechanism of refeeding-resistance, a core psychopathology relevant to 'ambivalent' eating behaviors, remains unclear in this disorder. Obestatin plays an important role in the regulation of growth hormone release, appetite, and energy metabolism. However, the progress of these patients and changes in the levels of obestatin during treatment were not reported. The purpose of this study was to determine the changes in obestatin levels when energy intake increases in AN-R patients. As a result, obestatin was higher in AN-R patients than in control subjects as well as acyl ghrelin and des-acyl ghrelin. An increase in the intake calorie has decreased obestatin as well as des-acyl ghrelin. These findings indicate that the obestatin is an important factor in the diagnosis and treatment of AN-R, similarly to acyl ghrelin and des-acyl ghrelin. In the future, the research on the clinical application of the ghrelin peptide family and the receptor will be expected to progress.