Fifteen minutes of vigorous exercise every day could cut the risk of breast cancer by one fifth, Oxford University research has found.
The study of 125,000 post-menopausal women found that those who did the most physical activity had a far lower chance of developing the disease than those who did the least exercise.
Women who did between 15 minutes and 35 minutes of vigorous exercise, such as running, every day were one fifth less likely to develop breast cancer, compared with those who took no vigorous exercise.
The study also found that women with the most body fat were 55 per cent more likely to develop the disease than the leanest women,
But being physically active helped reduce the risk of breast cancer regardless of a womanâ€™s weight.
The findings presented at the National Cancer Research Institute (NCRI) Cancer Conference today tracked the lifestyles of 125,000 women, of whom around 1,000 were diagnosed with breast cancer during three years of follow-up.
Lead researcher Professor Tim Key, a Cancer Research UK scientist from the Cancer Epidemiology Unit at Oxford University, said: â€œWeâ€™ve known for some time that exercise may help to reduce breast cancer risk after the menopause, but whatâ€™s really interesting about this study is that this 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.
â€œWe donâ€™t yet know exactly how physical activity reduces breast cancer risk, beyond helping to maintain a healthy weight, but some small studies suggest that it could be linked to the impact on hormone levels in the body.â€
One in eight women will suffer from breast cancer, and most cases are driven by the female hormone oestrogen and sensitive to the hormone progesterone.
In the study, women in the bottom physical activity quartile didnâ€™t do any vigorous physical activity, such as running or any activity that made them out of breath, although they may have done some walking and moderate physical activity.
Those in the top physical activity quartile did an average of at least 15 minutes of vigorous activity every day, such as running, with many doing up to 35 minutes a day, in addition to walking and moderate activity.
Alison Cox, Cancer Research UKâ€™s director of cancer prevention, said: â€œThis study confirms that the benefits of staying active go beyond just burning calories, sending a clear message to all women about the importance of being physically active throughout life.â€
The womenâ€™s body fat percentage and self-reported physical activity was tracked through UK Biobank â€“ a database of medical information and samples for researchers to study how human disease develops.
Nearest tube: Elephant & Castle underground station (Northern and Bakerloo lines).
Nearest Railway Station: Elephant & Castle
Buses from Elephant and Castle: ask bus driver for Burgess Park. Bus numbers: 12, 171, 148, 176, 68, 484, 42, 40, 45