Study to Evaluate Effectiveness of a Weight Loss Program in Obese Patients During 3 Months Prior to Bariatric Surgery

Study population: 25 patients with morbid obesity (BMI ≥ 40 kg / m2) or severe obesity (BMI 35 to 39.9 kg / m2) , with two or more comorbidities, scheduled for bariatric surgery within 3 months, and who will start treatment with the multidisciplinary weight loss program (PnK Method) based on diet, exercise and psychological support. Patients will be followed-up for 3 months, with the following controls: pre-selection, baseline, month 1, month 2, month 3, and control when hospital discharge. The treatment schedule in these patients will be as follows: a very low calorie ketogenic diet for at least 1 month or until losing 10% of the weight, and then, a low calorie diet with gradual reintroduction of natural foods for 2 months, until surgery. The investigators will obtain retrospective data from 25 patients treated with the standard diet who met the same inclusion/exclusion criteria as the patients in this study and who similarly resemble in age, sex and BMI, for comparative analysis (control group).