Humans with single nucleotide polymorphisms in the MC4R are morbidly obese, hyperphagic, and have elevated leptin levels and insulin resistance (Haskell-Luevano et al., 2009); those with deficiencies in the leptin or leptin receptor gene, or BDNF-related genetic polymorphisms also have hyperphagic obesity (Spaeth et al., 2012). Here, LEP is linked to Insulin resistance.