INS and type 2 diabetes mellitus: Our findings are consistent with the results from previous studies that found marked weight loss after RYGB improved β cell function, assessed as glucose-stimulated insulin secretion in response to a mixed-meal test, a graded glucose infusion protocol, or a hyperglycemic clamp procedure, in people with T2D but did not improve or even decreased β cell function 1–2 years after marked weight loss induced by RYGB in people without diabetes (6, 7, 16, 33).