Obesity is a chronic life-threatening disease, and bariatric surgery is the most effective treatment in those patients. The two main operations are laparoscopic sleeve gastrectomy (LSG) and Roux-en-Y gastric bypass (RYGB). LSG carries a smaller risk for nutritional deficiencies, while gastric bypass procedures are associated with increased nutritional deficiencies because the procedure is more complex and changes the gastrointestinal anatomy. Recent studies comparing LSG and RYGB have proven that these types of operation may lead to a similar weight reduction effect but cause different micronutrient deficiencies. Types of malnutrition after bariatric surgery include protein-energy malnutrition and deficiencies of micronutrients, such as iron, folate, vitamin A, and vitamin B-12. Bariatric patients who do not adhere to the recommended diets are at a greater risk of developing relevant malnutrition. Therefore, life-long postoperative clinical and laboratory monitoring is necessary to diagnose deficiencies of vitamins, trace elements, and minerals and to correct them with supplements. Unfortunately, no standardized aftercare regimes exist for these patients, and the costs for nutritional supplements are paid by the patients themselves. (C) 2019 S. Karger AG, Basel
