It has been suggested that factors and pathways associated with obesity, such as dysregulation of hormone biosynthesis and adipokine balance, abnormalities of the IGF‐I system and signaling, and increased production of inflammatory mediators may affect BC penetrance in women with BRCA1 or BRCA2 mutations by contributing to DNA damage, promoting cell proliferation, and interacting with hormone receptors. The gene discussed is NR4A1; the disease is obesity due to melanocortin 4 receptor deficiency.