A great deal of effort has been made for many years to explain the relationship between obesity and breast cancer. Molecularly, the relationship involves dynamic and complex interactions between a milieu of hormones, cytokines, adipokines, affecting cell signaling and potentially epigenetic pathways. Recently, studies in postmenopausal women have shown that weight loss modulates these cytokines and adipokines favorably. Inflammation associated with obesity can also be characterized pathologically when macrophages surround necrotic adipocytes in what are called crown-like structures (CLS). Furthermore, increased central obesity as measured by waist-to-hip ratios, may be associated with hypermethylation of certain breast cancer genes, and physical activity can reduce methylation of certain breast cancer-associated genes.