Practising sport for more than 60 minutes a day reduces the risk of developing breast cancer, and this applies to women of any age and any weight, according to a new study.

The research says exercise can benefit women of any age and any weight in protecting them against breast cancer.

Research presented to the 9th European Breast Cancer Conference (EBCC-9) in Glasgow found that compared with the least active women, those with the highest level of physical activity reduced their breast cancer risk by 12%.

Professor Mathieu Boniol, of the International Prevention Research Institute at Lyon, France, presented an analysis of 37 studies published between 1987 and 2013, which included over four million women.

"These are all the studies looking at the relationship between physical exercise and breast cancer risk that have been published to date, so we are confident that the results of our analysis are robust," he said.

Although the results varied according to cancer type, the overall message on the role of exercise in breast cancer prevention was encouraging, the researchers say.

The protective benefit was not seen in in women taking hormone replacement therapy (HRT). However, it is felt that increased awareness of the side effects of HRT means that its use is diminishing.

While the mechanisms for the protective effect of exercise on many cancers are unclear, they are largely independent of the body mass index (BMI) of the individual, so the effect is believed to be due to factors other than weight control.

"Adding breast cancer, including its aggressive types, to the list of diseases that can be prevented by physical activity should encourage the development of cities that foster sport by becoming bike and walk-friendly, the creation of new sports facilities, and the promotion of exercise through education campaigns," said Prof Boniol.