Transgenic mice overexpressing CYP7A1 in the liver have been reported to be resistant to high-fat diet induced obesity, fatty liver disease and diabetes (Li et al., 2010), while decreased CYP1B1 expression has been correlated with altered lipid metabolism, especially lysophosphatidylcholines, contributing to protection against the development of obesity (Li et al., 2014). Here, CYP1B1 is linked to obesity due to melanocortin 4 receptor deficiency.