UCP1 and obesity due to melanocortin 4 receptor deficiency: Lastly, but not least, we did not investigate the other candidate genes involved in vitamin D metabolism e.g. RXR nuclear receptor and genes contributing to obesity such as UCP1, UCP2, ADRA2B, ADRB3, LEPR, and ESR1 and their interaction with the VDR; these analyses may contribute to a better understanding of environmental and gene interactions.