Our data demonstrate that (a) PWL (6%, 11%, 16%), induced by a LCD, in people with obesity without diabetes causes a progressive decrease in insulin secretion in relation to plasma glucose; (b) marked (~20%) weight loss, induced by LAGB and RYGB, in people with obesity without diabetes does not alter insulin secretion in relation to plasma glucose; and (c) marked (~20%) weight loss, induced by a LCD alone or RYGB, causes a marked increase in insulin secretion in relation to plasma glucose, without a difference between the T2D-LCD and T2D-RYGB groups. Here, INS is linked to diabetes mellitus.