Impact of bariatric surgery and predictive factors for eating disorders before and after surgery: a prospective observational study

Morbid obesity is frequently associated with high-risk behaviors such as eating disorders (EDs). This study aimed to investigate the prevalence, changes, and predictive factors of EDs before and one year after metabolic and bariatric surgeries (MBS) in Iranian adults. This prospective observational study included 96 MBS candidates with class II (BMI 35–40 kg/m² with comorbidities) or class III obesity (BMI ≥ 40 kg/m²). Patients underwent sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), or one-anastomosis gastric bypass (OAGB). Demographic data, nutritional status [assessed by a food frequency questionnaire (FFQ)], BMI, and EDs symptoms were collected before and one year after surgery via the EDs Questionnaire (EDE-Q 6.0), and psychological status was assessed via the Symptom Checklist-90-Revised (SCL-90-R). A total of 22.9% of the participants were identified as having EDs. These individuals had a significantly higher BMI compared to those non-eating disorders (non-Eds) (49.9 ± 9.1 vs. 45.4 ± 5.8; p = 0.039). All MBS types (SG RYGB and OAGB) led to significant reductions in EDs global and subscale scores (p < 0.05), with SG surgery group showed notable numerical improvements in weight and shape concerns. Female sex (β = 0.87; p = 0.002) and younger age (β = − 0.03 per year; p = 0.014) were significant predictors of higher EDs scores after surgery. MBS reduce symptoms of EDs, with a trend towards SG showing the most prominent effect. Younger age and female sex were independently associated with greater severity of symptoms after surgery. These findings highlight the importance of targeted postoperative psychological support and underscore the interplay between biological and psychological factors. This study examined how EDs change in people with severe obesity before and after three types of MBS and what factors might influence these changes. We followed 96 Iranian adults who had undergone one of the three types of MBS. Before surgery, nearly one quarter of the participants presented signs of an EDs, and these individuals generally had greater body weights than did the other individuals. One year after surgery, EDs symptoms improved in most patients, with the greatest improvement observed in those who underwent SG. However, younger patients and women were more likely to continue experiencing some eating-related problems after surgery. These findings suggest that MBS can help reduce EDs symptoms, but ongoing psychological support, especially for younger patients and women, is essential for achieving better long-term outcomes.