VDR and obesity due to melanocortin 4 receptor deficiency: The potential mechanism of low 25(OH)D concentration in high body fat subjects could be: 1) sequestration of vitamin D by adipose tissue; 2) adipose tissue has both vitamin D receptors and 1-α-hydroxylase enzymes, which can synthesize 1,25-dihydroxyvitamin D; and, 3) vitamin D may regulate adipose tissue mass, differentiation, and metabolism; consequently, low vitamin D status might contribute to obesity [36,37].