Hence, this study investigated the following: (1) UCN3 levels in the blood and subcutaneous adipose tissue (SAT) from normal-weight and overweight individuals with and without T2D; (2) the association between UCN3 levels and physical, clinical, and biochemical markers; and (3) the effect of a 3-month physical exercise program on UCN3 levels in obesity and T2D. The gene discussed is UCN3; the disease is obesity due to melanocortin 4 receptor deficiency.