Of the 21 identified leptin-associated genes found to have an inverse relationship between the two dietary types (HFD, normal fat) Peli3, Creb1, Enpp2 and Centg1, four genes previously reported to play a role in obesity and colon-related diseases, were found to have either a positive or negative relationship between serum leptin or insulin concentration and consumption of either HFD or normal diet (304). Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.