In morbidly obese patients, i.e. body mass index ≥35, bariatric surgery is considered the only effective durable weight-loss therapy. Laparoscopic Roux-en-Y gastric bypass (LRYGBP), laparoscopic sleeve gastrectomy (LSG), and biliopancreatic diversion with duodenal switch (BPD-DS) are associated with risks of nutritional deficiencies and malnutrition. Therefore, preoperative nutritional assessment and correction of vitamin and micronutrient deficiencies, as well as long-term postoperative nutritional follow-up, are advised. Dietetic counseling is mandatory during the first year, optional later. Planned and structured physical exercise should be systematically promoted to maintain muscle mass and bone health. In this review, twelve key perioperative nutritional issues are raised with focus on LRYGBP and LSG procedures, the most common current bariatric procedures.