To assess how obesity impacts the lungs to facilitate metastatic colonization, 3-week-old female FVB/N mice were fed a LFD or HFD for 16 weeks and then Met-1 or TC2 tumor cells were injected into the tail vein to generate lung metastasis in the absence of a primary tumor. This evidence concerns the gene GZMM and obesity due to melanocortin 4 receptor deficiency.