Objective: Low BMI is a poor prognostic factor. Previous studies have reported that daily body activity (ADL) ability is difficult to improve if the body mass index (BMI) at admission is low, but the relationship between BMI at discharge and ADL ability has not been clarified. Therefore, we aimed to clarify that ADL ability is low when BMI at discharge is low. Subjects and methods:A cross-sectional study of patients who were admitted to an integrated community care ward and underwent rehabilitation. Patient information was investigated from medical records. BMI: Less than 20 kg/m 2 was defined as a low BMI group, and more than that was defined as a non-low BMI group. The survey items were compared between groups and at the time of hospitalization. We also investigated the relationship between functional independence rating scale (FIM) gain and discharge BMI by multiple regression analysis. Results:The number of subjects was 200, 103 in the low BMI group, and 97 in the non-low BMI group. The low BMI group had a lower total FIM score and total FIM gain than non-low BMI, and BMI was low since admission (p < 0.05). Multiple regression analysis showed that discharge BMI was independently positively related to total FIM gain (p < 0.05). Conclusion:It was suggested that BMI may be related to the improvement of ADL ability.