Bariatric surgery outcomes in multiple sclerosis: Interplay with vitamin D and chronic pain syndromes

•Bariatric surgery is effective and safe with multiple sclerosis patients.•There was no significant change in neurologic function due to bariatric surgery.•Vitamin D levels increased post-surgery.•Those patients who failed to lose significant weight from surgery had chronic pain syndromes and were on gabapentin. Obesity and lower vitamin D levels are associated with adverse outcomes in multiple sclerosis (MS). Bariatric surgery is a safe intervention in patients with MS, although it lowers vitamin D levels in the general population. To investigate the effects of bariatric surgery on vitamin D levels and interrogate risk factors for unsuccessful post-operative weight loss in patients with MS. We retrospectively identified patients with MS who underwent bariatric surgery from 2001 to 2023. Wilcoxon signed rank tests for paired samples were used to compare pre- and post-operative body mass index (BMI), expanded disability status scale (EDSS), timed 25-foot walk (T25FW), and median vitamin D values. Following bariatric surgery, patients with MS had a decrease in BMI (mean percent total weight loss of 18.4 %, range 0–38 %, p