Purpose: The purpose of this study was to evaluate changes in non-alcoholic fatty liver disease (NAFLD) after laparoscopic sleeve gastrectomy (LSG) using computed tomography (CT) images. Methods: We analyzed data from 57 patients who underwent LSG and had CTs performed before and after surgery. The patients included 34 women and 23 men (with an average age of 43 years); their mean preoperative weight and body mass index were 120 kg and 46 kg/m2, respectively. Obesity-related health disorders included type 2 diabetes mellitus (T2DM) in 33 patients, hypertension in 33 and dyslipidemia in 32. We diagnosed NAFLD in cases with liver to spleen ratios (L/S ratio) <0.9 on non-contrast CT images. We evaluated changes in body weights, BMIs, comorbidities, metabolic parameters, L/S ratios, and liver volumes after surgery. Results: The mean interval between CT scans before and after surgery was 26 months. The total weight loss and % excess weight loss were 35 kg and 72%, respectively. The remission rates for T2DM, hypertension, and dyslipidemia were 85%, 76% and 84%, respectively. After LSG, the L/S ratio increased in all the patients, while all except for one had L/S ratio >0.9. We diagnosed 33 out of 57 patients (58%) as having NAFLD before the operation. After the operation, the L/S ratios and liver volumes were not statistically different between the patients with previous NAFLD and those without it. Conclusion: Laparoscopic sleeve gastrectomy is an effective treatment for obesity-related health disorders including NAFLD in Japanese obese patients.