INS and obesity due to melanocortin 4 receptor deficiency: The effect of marked (16%–25%) weight loss on insulin-stimulated glucose disposal rate in relation to FFM during the hyperinsulinemic-euglycemic clamp procedure, which provides an index of skeletal muscle insulin sensitivity (13), was used to identify Responders and Non-responders among 43 women with class II and class III obesity (body mass index ≥35 kg/m2).