Due to the reduced volume and postoperative gastric edema, ingestion of solid foods in the first few days after surgery is very difficult or impossible; following bariatric surgery there are anatomical changes in the vagus that may contribute to the alteration of taste perception. In order to facilitate patient weaning and improve the liking of the foods used in this semi-liquid phase, our Center intends to test some "Foods for Special Medical Purposes" (AFMS), in order to ensure a better intake of nutrition, including in terms of vitamin D3 and calcium, good palatability and thus a better adherence to the recommended nutritional indications in the immediate postoperative period than the homogenized foods used in the standard diet.

Primary goal: Patient compliance throughout the weaning period (4 weeks postintervention), assessed through product liking measurable by Sensory Questionnaire.

Secondary objective:

• Patient compliance throughout the weaning period (4 weeks postintervention), assessed through product liking measurable with test comparative

• Taste perception, liking, palatability and food preferences among the different products (Special Medical Purpose Foods-AFMS vs homogenized foods) and between pre and post bariatric surgery.

• Nutritional efficacy (assessment of blood levels of micronutrients such as. iron, ferritin, transferrin , calcium, vit D3, folic ac, vit B12 and of macronutrients such as total protein and protein electrophoresis; bioimpedance analysis for body composition assessment).

  32 subjects with severe or morbid obesity ( BMI ≥ 35 kg/m2 in the presence of comorbidities and BMI ≥ 40 kg/m2 , respectively), male and female, candidates for bariatric surgery (Sleeve Gastrectomy and Roux-en-Y Gastric Bypass).

Two timepoints: T0 (pre-rev) and T1 (follow-up 1 month +/-7 days). Planned assessments at T0 and T1.

• Administration of the sensory questionnaire.
• Comparative test
• Hematochemical tests: iron, ferritin, transferrin, , vit D3, ac. Folic, vit B12 and macronutrients such as total protein + general hematochemicals (complete blood count complete, protein electrophoresis, AST, ALT, gamma GT, creatininemia, azotemia, col tot, HDL, LDL, triglycerides, blood glucose).
• Analysis of taste perception and variation by Taste Strips.
• Bioimpedance analysis (BIA)
• Anthropometric evaluations

Inclusion Criteria:

• Age ≥18 and ≤ of 60
• Subjects with severe or morbid obesity (BMI ≥ 35 kg/m2 in the presence of comorbidities and BMI ≥ 40 kg/m2)
• Absence of diagnosis of primary obesity
• Absence of medical/psychiatric contraindications
• Signature of informed consent for the study
• Patients who are candidates by clinical practice for bariatric surgery (Sleeve Gastrectomy and Roux-en-Y Gastric Bypass).

Exclusion Criteria:

• Presence of chronic diseases of the digestive system, such as chronic diseases intestinal, malabsorption syndrome, diverticulosis of the colon
• Current pregnancy (verified by self-declaration) and/or lactation
• Subjects with endocrine disorders (e.g., Cushing's m., thyroid disease uncontrolled)
• Presence of known renal insufficiency or creatinine levels greater than 1.8 mg/dl and eGFR < 60 ml/min
• Presence of malignant pathology
• Alcohol or drug abuse
• Severe psychological/psychiatric disorders
• Difficulty adhering to the protocol due to language barriers or other reasons.