Gaining even a moderate amount of weight after menopause could increase the risk of breast cancer, says a study.
Researchers led by Heather Ellassen, Brigham, and Women's Hospital studied over 87,000 women, aged 30 to 55 years for up to 26 years. Their weight at age 18 was recorded and noted how it had changed since, reported the online edition of BBC News.
Around 50,000 of the women who went through menopause during the course of the study were also assessed for weight change.
It was found that women who gained about 55lb (25 kg) or more after the age of 18 had a 45 percent increased risk of developing breast cancer compared with those who maintained their weight, the researchers said.
They said that 15 percent of the study's breast cancer cases could be attributed to weight gain of 4.4lb (2 kg) or more since the age 18.
Putting on 22lbs (9.9 kg) increased a woman's risk of developing the disease by 18 percent, the US team writing in the Journal of the American Association said.
But those who had lost the same amount cut the risk by 57 percent, they said.
The researchers said weight loss after menopause lowers levels of estrogen hormones, which are linked to breast cancer, cutting the risk of the disease.