Objective:To investigate the influencing factors of operation time for laparos-copic sleeve gastrectomy (LSG) and analyze the learning curve of LSG in sarcopenic obesity (SO) and non-sarcopenic obesity (NSO).Methods:The retrospective cohort study was conducted. The clinical data of 240 obesity patients who underwent LSG in the Fujian Medical University Union Hospital from January 2018 to June 2022 were collected. There were 52 males and 188 females, aged (30±8)years. Patients underwent L3 vertebral body horizontal axial computer tomography (CT) scanning before and after receiving LSG to accurately segment muscles and fats. Observation indicators: (1) treatment and follow-up; (2) influencing factors of operation time for LSG; (3) cumulative sum (CUSUM) of learning curve; (4) comparison of clinical data between patients in the initial and profi-cient stages. Measurement data with normal distribution were represent as Mean± SD, and comparison between groups was conducted using the t test. Measurement data with skewed distribution were represented as M(IQR), and comparison between groups was conducted using the non-parameter test. Count data were described as absolute numbers, and comparison between groups was conducted using the chi-square test. Univariate and multivariate analyses were conducted using the Logistic regression model. The CUSUM of learning curve was calculated and the fitting process was conducted on scatter plot of learning curves. Results:(1) Treatment and follow-up. Of the 240 patients, there were 97 cases of SO and 143 cases of NSO. All 240 patients underwent LSG successfully, without conversion to open surgery. The operation time of 240 patients was (108±23)minutes. None of patient died during the perioperative period and all patients underwent follow-up during the postoperative 6 months. (2) Influencing factors of operation time for LSG. Results of multivariate analysis showed that SO was an independent factor influencing operation time for LSG ( odds ratio=2.207, 95% confidence interval as 1.207-4.038, P<0.05). (3) CUSUM of learning curve. Results of CUSUM of operation time in patients of SO and NSO showed that the best fit equation of patients of SO was y=-4E-08x 6+1E-05x 5-0.001 1x 4+0.063 1x 3-1.89x 2+28.126x-48.671 (x means the number of surgical cases), with goodness-of-fit R 2 as 0.833, and the best fit equation of patients of NSO was y=3E-09x 6-1E-06x 5+0.000 2x 4-0.010 9x 3+0.063 8x 2+12.053x-65.025 (x means the number of surgical cases), with goodness-of-fit R 2 as 0.716. Based on the trend of CUSUM of learning curve of operation time, the peak value of number of surgical cases in patients of SO and NSO was 81 and 36, respec-tively, which was used to divide the learning curve as two stages of the initial stage and the proficient stage. (4) Comparison of clinical data between patients in the initial and proficient stages. ① Of the 97 patients of SO, there were 81 cases and 16 cases in the initial stage and the proficient stage of LSG, with the operation time, postoperative duration of hospital stay as (119±23)minutes, (5.9±2.3)days and (106±21)minutes, (4.7±0.5)days, showing significant differences between them ( t=2.074, 2.147, P<0.05). ②Of the 143 patients of NSO, there were 36 cases and 107 cases in the initial stage and the proficient stage of LSG, with gender (female), height, preoperative body mass, defatted body mass, operation time, postoperative duration of hospital stay, body mass at postoperative 6 month, body mass index (BMI) at postoperative 6 month, percentage of excess weight loss (EWL%) at postoperative 6 month, cases with EWL% >100% at postoperative 6 month, excess BMI at post-operative 6 month as 20, (170±10)cm, (110±25)kg, (57±12)kg, (108±22)minutes, (6.1±1.6)days, (80±16)kg, (27.63±4.22)kg/m2, 83%±35%, 9, 1.99(6.03)kg/m2 and 87, (164±8)cm, (99±20)kg, (52±12)kg, (100±19)minutes, (4.7±1.1)days, (71±16)kg, (25.89±4.48)kg/m2, 103%±42%, 48, 0.31(5.82)kg/m2, showing significant differences between them ( χ2=9.484, t=3.266, 2.424, 2.141, 2.137, 5.821, 2.740, 1.993, -2.524, χ2=4.432, Z=-2.300, P<0.05). Conclusions:SO is an independent factor influencing operation time for LSG. It is suggested that the surgeons need to finish 81 cases and 36 cases master LSG in patients of SO and NSO.