Predictors of Weight Loss and Metabolic Health After Bariatric Surgery

Inclusion Criteria: * Ability to provide informed consent * Patient is ≥ 18 and ≤ 75 years old * BMI ≥ 40 kg/m2 or ≥ 35 kg/m2 with obesity related comorbidity * Scheduled for primary bariatric procedure: Roux-en-Y gastric bypass (RYGB) or Sleeve Gastrectomy (SG) * Stable weight 3 months prior to inclusion weight (\<10% change in body weight for 3 months prior to assessments) In order to be eligible to participate in the subgroup of this study, we will use the following inclusion criteria: * Ability to provide informed consent * Patient is ≥ 18 and ≤ 75 years old * BMI ≥ 40 kg/m2 or ≥ 35 kg/m2 with obesity related comorbidity * Patients scheduled for RYGB * Patients who are insulin resistant (impaired fasting glucose (\> 5.6 mmol/L) or fasting insulin \> 74 pmol/L) * Postmenopausal women (to prevent bias due to the effect of sex hormones on insulin sensitivity) Exclusion Criteria: * Any actual medical condition except for obesity related health issues or well treated hypothyroidism * Pregnancy anticipated in the first two years following surgery A potential subject who meet the following criteria will be excluded from participation in the subgroup of this study: * Coagulation disorders and/or use anticoagulants * Use of any medication except for statins, antihypertensives (except for Angiotensine converting enzyme (ACE)- or angiotensin receptor blockers) and thyroid hormone * Diabetes mellitus type 2