Study to Evaluate the Pharmacokinetics of Vitamin D (Cholecalciferol) in Patients Undergoing Obesity Surgery in a Deficit Situation and After Standardization

Set the pattern of vitamin D supplementation in obese patients undergoing bariatric surgery in deficit of vitamin D. Patients receive a single oral dose of vitamin D, during the 28 days will be done a kinetic curve. Then and over the next 3 months, levels are normalized. Once normalized, will be administered another single oral dose to a second pharmacokinetic evaluation.