Comparative Analysis of Postoperative Hair Loss and Micronutrient Deficiencies After One-Anastomosis Gastric Bypass Versus Sleeve Gastrectomy.

PURPOSE: Hair loss is a frequent but distressing complication after metabolic and bariatric surgery (MBS), often attributed to nutritional deficiencies. Comparative evidence between one-anastomosis gastric bypass (OAGB) and laparoscopic sleeve gastrectomy (LSG) is limited. This study aimed to evaluate postoperative hair loss and its association with micronutrient changes at 3 and 6 months following OAGB and LSG. METHODS: In this prospective cohort, 261 patients (LSG, n = 117; OAGB, n = 144) were followed between 2021 and 2024. Hair loss was assessed using the standardized hair pull test at baseline, 3 months, and 6 months. Serum iron, zinc, folic acid, and vitamin B12 were measured at the same intervals. Generalized linear mixed models and regression analyses were applied to assess longitudinal changes and predictors of hair loss. Logistic regression with ROC analysis was used to evaluate model performance. RESULTS: Hair loss scores increased significantly at 3 months (p < 0.001), peaking at this time point before improving slightly at 6 months ( p = 0.274 vs. 3 months). Trends were similar in both groups, with no significant difference in hair loss between OAGB and LSG (interaction p = 0.572). Serum iron and zinc declined significantly at 3 months with partial recovery by 6 months, whereas vitamin B12 and folic acid increased with routine supplementation. Reduced iron levels were strongly associated with increased hair loss at both 3 and 6 months (p < 0.01), while zinc, folate, and vitamin B12 showed no consistent associations. In multivariable analysis, female sex, lower baseline iron levels, and lower baseline zinc levels independently predicted hair loss at 6 months. The predictive model demonstrated acceptable discriminative ability (AUC = 0.768, sensitivity 89%, specificity 75%). CONCLUSION: Postoperative hair loss peaks at 3 months and improves by 6 months, with comparable outcomes between OAGB and LSG. Iron deficiency and female sex were the strongest predictors of hair loss, underscoring the need for proactive nutritional monitoring. With appropriate supplementation, telogen effluvium can be managed as a temporary and reversible complication of MBS.