Although some similarities in the findings compared with a previous study were noted herein, the lack of induction of CYP1A1 in lean mice, or EPHX1 or GSTM in either mouse group by DMBA exposure and no observation of basally higher EPHX1, suggests a difference in the obesity experimental paradigm (hyperphagia in KK.CG-Ay/J mice vs diet induced in wild-type C57Bl6/J mice) impact on ovarian chemical biotransformation. This evidence concerns the gene GSTM2 and obesity due to melanocortin 4 receptor deficiency.