Obesity increases the risk of death in both premenopausal and postmenopausal patients with breast cancer, but the effects of obesity on the risk of breast cancer in premenopausal (lower risk of ER-positive breast cancer) and postmenopausal (markedly higher risk of ER-positive breast cancer) women differ based on estrogen receptor (ER) status [29,30]. This evidence concerns the gene ESR1 and obesity due to melanocortin 4 receptor deficiency.