Background: Bariatric surgery is an alternative treatment for obesity. However, physicians need to be aware of the possible consequences of nutritional deficiencies with this type of surgery. This study aimed to determine the prevalence of inadequacy of macro-and micronutrients from the diet in patients undergoing Roux-en-Y gastric bypass after 3, 6, and 12 months postoperatively. Methods: We performed a longitudinal, observational, clinical study during preoperatively and 3-, 6-, and 12-month postoperatively (n = 95 patients). We collected information from medical records of patients in a Reference Clinic of Bariatric Surgery. Quantitative food intake was analyzed by ADS Nutri ® and Multiple Source Method ® software. The obtained data were compared with the daily-recommended intake in accordance with specific guidelines for bariatric surgery. Data were analyzed using t-tests, MannWhitney test, one-way analysis of variance (ANOVA), and Tukey's test. Results: There was a high prevalence of inadequacy of macronutrients and micronutrients from food in the postoperatively period. However, only vitamin B12 intake was adequate based on the daily recommended intake. Conclusions: Our study suggests that the intake of nutrients by feeding is below current recommendations. Individual nutritional counseling with a therapeutic plan for adequate nutrition and prescription supplements are important to ensure that nutritional recommendations are adhered to.