The basal plasma ICR was higher (P < 0.05) in the lean group than in any of the obese groups and was not different among the obese groups (Table 1); the basal ICR directly correlated with insulin sensitivity in the entire study population (r = 0.64; P < 0.05) and among only lean participants (r = 0.48; P < 0.05) or only participants with obesity (r = 0.60; P < 0.05) (Supplemental Figure 1B). Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.