The cancer researchers in U.K say that obesity is the biggest driving force behind the most common form of breast cancer in older women. Alcohol and cigarettes are the next largest culprits. Data shows that one in eight women in the U.K develops breast cancer in their lifetime and the majority of these tumours are hormone sensitive meaning their growth is fuelled by hormones. Too much stored fat in the body raises the level of these “sex” hormones.Studies show that post-menopausal women with high levels of estrogen and testosterone have between two and three times the risk of breast cancer than women with the lowest levels. Experts have known for some time that factors that influence hormone levels like pregnancy, the oral contraceptive pill and the menopause can change a woman's breast cancer risk.