Introduction: This study aimed to determine the effects of Stored Energy on changes in body weight (BW) and skeletal muscle mass (SMM) in patients with post-acute stroke and sarcopenia. Methods: This retrospective cohort study included patients with stroke and sarcopenia consecutively admitted to a Japanese rehabilitation hospital between 2015 and 2022. Sarcopenia was diagnosed based on the Asian Working Group for Sarcopenia in 2019 criteria. Total Stored Energy (kcal) was defined as total energy intake minus total energy requirements during hospitalization, and energy requirements were estimated as actual BW (kg) × 30 (kcal/day). Multiple regression analysis was used to adjust for the effects of confounders and to analyze the association between Total Stored Energy divided by length of hospital stay (= Stored Energy) and changes in BW and SMM during hospitalization. Results: Of the total 556 patients, 193 patients (mean age, 80 years; 43% male) were analyzed. The median (IQR) Total Stored Energy was -1544 (-18524, 16566) kcal and Stored Energy was -23 (-169, 165) kcal/day; 90 patients had Stored Energy > 0. Multiple linear regression analysis showed that Stored Energy was independently and positively associated with BW gain (β=0.412, P<0.001) and SMM gain (β=0.263, P<0.001). Conclusion: Stored Energy has a positive impact on BW and SMM in patients with post-acute stroke and sarcopenia.