Nutrology based on the analysis of benefits and harms generated by the ingestion of nutrients and assessing individual organic needs promotes the maintenance of health and the reduction of disease risk, as well as the treatment of manifestations of deficiency or excess. Obesity is defined by a body mass index greater than 30 kg/m². Its manifestation is the sum of genetic and environmental factors, this through sedentary lifestyle and caloric intake greater than energy consumption. There are many ways to deal with obesity, from behavioral changes such as a balanced diet and physical exercises, pharmacological and even surgical measures of different modalities, with Roux-en-Y gastric bypass surgery being the most used technique in Brazil. The most common postoperative nutritional deficiencies are iron, protein, calcium, folate, thiamine, zinc, copper, and vitamins D, B12, A, C, and K. In this case, we present the importance of nutrology in monitoring patients after bariatric surgery. This research made use of a bibliographic survey, giving priority to articles dated from the last 5 years, using the databases Lilacs, Medline, bireme, where articles, dissertations, and theses were consulted, in search of the following keywords, obesity, bariatric surgery, and nutritional deficiency, post-bariatric feeding.