Bariatric surgery has the unique ability to drive substantial and sustainable weight loss in people living with obesity. Non-reversibility of these surgical techniques provides lifelong benefits but entails the need for continuous medical follow-up. The purpose of the current paper is to review and summarize current data on nutritional deficiencies in patients before and after bariatric surgery. The cornerstone of preventing the emergence of disorders related to nutritional deficiencies is preoperative screening and correct supplementation since they may be exacerbated postoperatively. Following guidelines in conjunction to a lifelong personalized medical approach is of high importance. Bariatric surgery is a well-studied successful and durable means of weight loss that may lead to nutritional deficiencies. There is, thus, a medical need for careful monitoring and treatment of micro- and macronutrient deficiencies by an experienced multidisciplinary team.