It's an important discovery. Although it has always been known that being overweight or obese raises the chances for breast cancer, nobody was sure if shedding the pounds would reduce the risk.
There seems to be a direct link between the amount of weight lost and the reduction in risk, with women who lose the most weight also reducing their risk the most. The greatest risk reduction was 26 percent for those who lost 9kg or more (20-plus pounds), but women who lost much less—between 2 and 4.5kg (4.4 to 10 pounds)—still reduced their risk by 13 percent.
But weight loss had no effect on women who were taking HRT (hormone replacement therapy) after the menopause; their risk remained the same, reinforcing earlier studies that found the drug is an independent risk factor for breast cancer.
With more than two out of every three American women overweight or obese, losing weight is a simple and effective way to reduce rates of breast cancer, say researchers from the Harvard T H Chan School of Public Health.
They had analysed 10 studies involving more than 180,000 women who were aged 50 and older.