This is a descriptive, observational, longitudinal trial where the metabolism of the Roux limb of the small intestine will be analyzed in patients who have had RYGB. This analysis will include the time course of its adaptive changes in patients with Class II and Class III obesity who have T2D or people who do not (study groups). It is hypothesized that intestinal remodeling and metabolic reprogramming lead to increased metabolic activity and fuel utilization by the reconfigured intestine in humans and accounts, in large part, for the improvement in glucose homeostasis after RYGB in surgery in patients with T2D.