WOMEN who exercise moderately may be less likely than their inactive peers to develop breast cancer after menopause.
US researchers, whose study was published in the journal Cancer, found that of more than 3,000 women, those who'd exercised during their childbearing years were less likely to develop the cancer after menopause.
The same was true when women took up exercise after menopause, said the group, led by Lauren McCullough at the University of North Carolina, Chapel Hill.
"What we can say is, exercise is good for you," McCullough said.
"It's never too late to start. Our evidence suggests that if you start after menopause, you can still help yourself."
The findings add to a number of past studies tying regular exercise to lower breast cancer rates. But all the studies only point to a correlation and don't prove that exercise itself reduces women's breast cancer risk.
But excess body fat is related to higher levels of certain hormones, including estrogen, as well as substances known as growth factors which can feed tumour development.
And exercise might also have direct effects by boosting the immune system or the body's ability to clear cell-damaging "free radicals".