Objective To investigate the related risk factors of hair loss in obese patients after laparoscopic sleeve gastrectomy (LSG).Methods The retrospective case-control study was conducted.The clinical data of 54 obese patients who underwent LSG in the East Hospital of Tongji University between November 2013 and June 2015 were collected.All the patients received LSG,and postoperative hair loss of patients was observed.Factors affecting postoperative severe hair loss were analyzed,including gender,age,preoperative body mass index (BMI),postoperative excess weight loss (EWL),total bilirubin (TBil),albumin (Alb),hemoglobin (Hb),iron,zinc,copper,folic acid,vitamin B12 and vitamin D.Observation indicators:(1) follow-up and postoperative hair loss situations:cases with follow-up,follow-up time,cases with hair loss,severity of hair loss,time of hair loss,treatment of hair loss;(2) univariate analysis affecting severity of hair loss after LSG;(3) multivariate analysis affecting severity of hair loss after LSG.Follow-up using outpatient examination and Wechat was performed to detect the changes of BMI and hair loss up to September 2016.Measurement data with normal distribution were represented as (x)±s and comparison between groups was done by the t test.Comparison of count data was analyzed by the chi-square test.Multivariate analysis was done using the Logistic regression model.Results (1) Follow-up and postoperative hair loss situations:all the 54 patients were followed up for 15 months.Forty-two patients had hair loss,including 21 with slight hair loss,10 with moderate hair loss and 11 with severe hair loss.A proportion of hair loss was 6/11 in male and 36/43 in female.The onset time and end time of hair loss were (3.4± 1.4) months and (9.0± 3.6) months,respectively.Of 42 patients,15 took oral medication (6 with ferrous sulfate,5 with decavitamin and 4 with zinc gluconate oral solution) against hair loss,with no obvious improvement.During the follow-up,42 patients stopped hair loss and gradually grow new hair.(2) Univariate analysis affecting severity of hair loss after LSG:gender,postoperative EWL and folic acid were factors affecting severity of hair loss after LSG (x2 =5.161,t =-5.114,4.266,P＜0.05).(3) Multivariate analysis of affecting severity of hair loss after LSG:postoperative EWL and folic acid were independent factors affecting severity of hair loss after LSG (OR=1.039,0.499,95％ confidence interval:1.011-1.068,0.300-0.802,P＜0.05).A prediction accuracy of severity of hair loss after LSG was 85.2％.Conclusion Postoperative EWL and folic acid are independent factors affecting severity of hair loss after LSG.