CuD subjects In order to be enrolled into the CuD Arm, subjects who have had RYGB surgery will be recruited and screened for eligibility (inclusion and exclusion criteria below). Subjects whose plasma copper concentrations are in the deficient range (less than 80 μg/dL for women and less than 70 µg/dL for men, and/or ceruloplasmin activity below 62 units/L-1) following 4 weeks of supplementation with the RDA for copper will be eligible. Such supplementation is the routine standard of care with all patients undergoing RYGB surgery. This process aims to exclude patients who were only marginally copper deficient and not in need of sustained copper therapy. Subjects will be notified about their copper status by a study physician. They will be contacted by the study team, and their willingness to participate in the study will be determined.