Purpose In our centre, specialized high dose multivitamin supplementation designed to meet the needs of patients after gastric bypass surgery is routinely recommended in the early postoperative period. The aim of the present study was to analyse whether iron supplementation prescribed in clinical practice is sufficient in both sexes and whether multivitamin supplementation standardized for women might potentially lead to iron overload in men. Materials/Methods This was a retrospective study covering the period up to 36 months after bariatric surgery. Three groups were compared (men, premenopausal and postmenopausal women). The iron status was evaluated employing serum ferritin concentrations. Results A total of 283 patients who had at least one follow-up visit between January 2015 and April 2018 at a specialized academic outpatient centre were included (71 men, 130 premenopausal women, 82 postmenopausal women). Thirty-six months after surgery, 33.3%, 68.4% and 54.5% of the men, pre- and postmenopausal women, respectively, were iron deficient. The preoperative prevalence of excess ferritin levels was 13.7% in premenopausal, 3.0% in postmenopausal women, 5.7% in men and declined in the following months. Conclusion Iron deficiency is very common after gastric bypass surgery, and even high dosages of multivitamin and mineral supplements might not be sufficient to prevent the development of iron deficiency. Men, pre- and postmenopausal women differ in their prevalence of iron deficiency which demands adapted iron dosage regimens based on the sex and the age. Iron overload is rare in all observed groups and highest in premenopausal women. Graphical abstract

Introduction There is a growing number of patients undergoing bariatric surgery requiring lifelong follow-up. Therefore, follow-up care can no longer be covered by specialized outpatient clinics alone due to the sharp rise in the number of bariatric patients. BagEL (Bariatric Patients in Primary Care: Post-operative Nutrition and Lifestyle Management) is a survey to evaluate a newly developed structured disease management program including nutrition and lifestyle management in primary care. Methods The study is conceived as a randomized cohort study with a control group. An expert questionnaire for general practitioners (GPs) was developed to assess the usability of a structured post-operative care system regarding nutrition and lifestyle management for bariatric patients in primary care. A structured follow-up program in primary care with a so-called “bariatric monitoring passport” (BMP) was provided for patients in the intervention group (INT) and the existing information sheet “Metabolic surgery and perioperative care” for the control group (CON). 124 patients, who met inclusion criteria and who underwent a bariatric procedure first time, served as ambassadors for delivery of the expert questionnaire and study documents to their individual GPs. Results A total of 39 (31,5%) different GPs from 124 ambassador patients responded. For the primary outcome “Does the aftercare-booklets support treatment of bariatric patients?” GPs of the INT group rated the new designed aftercare booklet (INT) significantly more helpful for treating bariatric patients than the one from the CON group (p=0,041). Discussion/Conclusion These results suggest that GPs are welcoming supportive tools like our BMP to improve the care of long-term follow-up of bariatric patients and should actively participate in the development of lifelong disease management plans necessary to cope with the rapidly growing number of patients.