Half an hour of exercise daily helps middle-aged women not only in preventing weight gain but also in cutting down the risk of breast cancer by 21 percent, says a new Oxford University research.
The study revealed that women who indulged in 15 minutes to 35 minutes of vigorous exercise showed one fifth less chance of developing breast cancer, compared with those who avoided vigorous exercise.
The research followed 125,000 post-menopausal women for three years.
Researchers pointed out that aggressive physical activity decreases the level of oestrogen in the body. And it has been proved that oestrogen promotes tumour growth in the body.
Oxford University researchers also concluded that obese or overweight women have over 50 percent more chance to develop breast cancer than those who are thin because more fat cells means more oestrogen.
"What's really interesting about this study is that (reduction in breast cancer risk) does not appear to be solely due to the most active women being slimmer, suggesting that there may be some more direct benefits of exercise for women of all sizes," said Professor Tim Key, a Cancer Research UK scientist from Oxford University.
One in eight women in the United States will get breast cancer some time in their life, says the American Cancer Society.
The exercise can be in the form of aerobics, Zumba or step classes, playing squash or joining a spinning class. But scientists have said that running is more beneficial than simple walking.
Alison Cox, head of cancer prevention at Cancer Research UK, said this study "confirms that the benefits of staying active go beyond just burning calories".