INS and obesity due to melanocortin 4 receptor deficiency: Before the VLCKD treatment, the serum concentrations of 25(OH)D of the persons with obesity were significantly correlated with both FM–kg (r = −0.40; p < 0.05) and BMI (r = −0.47; p < 0.01) but not with body weight, body circumferences, WHR, RA, CR, serum insulin concentrations or HOMA-IR (p = not significant) (Figure 1).