Background Roux-en-Y gastric bypass (GBP) and sleeve gastrectomy (SG) have increased dramatically, potentially increasing the prevalence of nutritional deficiencies. The aim of this study was to analyze the effects of food restriction during the first year after bariatric surgery (BS) on nutritional parameters. Methods Twenty-two and 30 obese patients undergoing GBP and SG were prospectively followed at baseline and 3, 6, and 12 months after BS (N = 14 and N = 19 at T12). We evaluated food intake and nutrient adequacy (T0, T3, T12), as well as serum vitamin and mineral concentration (T0, T3, T6, T12). Results At baseline, GBP and SG patients had similar clinical characteristics, food intake, nutrient adequacy, and serum concentration. The drastic energy and food reduction led to very low probabilities of adequacy for nutrients similar in both models (T3, T12). Serum analysis demonstrated a continuous decrease in prealbumin during the follow-up, indicating mild protein depletion in 37 and 38 % of GBP patients and 57 and 52 % of SG patients, respectively, at T3 and T12. Conversely, despite the low probabilities of adequacy observed at T3 and T12, systematic multivitamin and mineral supplementation after GBP and SG prevented most nutritional deficiencies. Conclusions GBP and SG have comparable effects in terms of energy and food restriction and subsequent risk of micronutrient and protein deficiencies in the first year post BS. Such results advocate for a cautious monitoring of protein intake after GPB and SG and a systematic multivitamin and mineral supplementation in the first year after SG.