Even moderate weight loss can significantly reduce levels of circulating oestrogens which are associated with an increased risk of breast cancer, US researchers have found.

Results suggested that losing just five per cent or more of one's weight could cut by a quarter to a half the risk for the most common, oestrogen-sensitive breast cancer said researcher, director of the Prevention Centre at Fred Hutchinson Cancer Research Centre, Dr Anne McTiernan.

The study in 439 overweight to obese sedentary women aged 50 to 75 was the first to show that losing weight through a healthy diet significantly lowered blood oestrogen levels in postmenopausal women and led to average weight losses of 10 percent of their starting weight. The most striking effect was if diet was combined with exercise.

"This shows that it's never too late to make lifestyle changes to reduce your risk for breast cancer," Dr McTiernan said.

Women who have had a hysterectomy and who use oestrogen-only hormone replacement therapy appear less likely to develop breast cancer in the long term than women who have never used HRT, new findings published by the Lancet today, Wednesday 7 March 2012, indicate.

Researchers followed postmenopausal women for nearly 12 years and found a 23% reduction in the incidence of invasive breast cancer in those who had used conjugated equine oestrogen therapy for an average 5.9 years, compared with women on placebo.

Those on oestrogen therapy who did develop breast cancer were also much less likely to die from the cancer than women who developed breast cancer in the placebo group.