For women over 50, shedding a few pounds may reduce breast cancer risk. But the story may be different for women in their 20s, 30s and 40s.
An international study of more than 600,000 women published in the International Journal of Cancer finds that women who gain weight from age 18 into their 40s and even a little later are less likely to develop breast cancer before hitting menopause, reports The Institute of Cancer Research. The research adds to existing evidence that being on the heavier side as a young adult reduces a woman’s chances of being diagnosed with premenopausal breast cancer.
For their analysis, researchers investigated the effect of weight gain on the risk of breast cancer before menopause using different age intervals. Women were followed for about 10 years on average.
Breast cancer before menopause is still relatively rare. Of the 600,000 women studied over 10 years, 10,886 developed breast cancer before menopause.
A weight gain of 10 kilograms—about 22 pounds—or more from early adulthood was associated with a reduced risk of breast cancer. For each 5kg gained (11 pounds), women between ages 18 to 24 and 45 to 54 saw their risk of breast cancer reduced by 4%, while those between ages 35 to 44 saw their risk decrease by 3%.
However, gaining weight starting at ages 35 to 44 onward did not affect women’s likelihood of getting breast cancer before menopause, which suggests that it is putting on extra pounds over time that is linked to decreased premenopausal breast cancer risk. In addition, after taking women’s starting weight into account, losing 11 pounds or more was not associated with premenopausal breast cancer risk.
Study authors believe that changes in breast composition during puberty may affect a woman’s weight in early adulthood, which in turn may affect her chances of developing premenopausal breast cancer. The authors also emphasize that strong evidence suggests that weight gain after menopause is associated with an increased risk for breast cancer after menopause.
“Women shouldn’t consider gaining weight as a way to prevent breast cancer—but understanding the biological reasons behind the link between weight and breast cancer risk could in the future lead to new ways to prevent the disease,” said study lead author Minouk Schoemaker, PhD, a senior staff scientist in cancer epidemiology at The Institute of Cancer Research, London.
For related coverage, read “Teenage Obesity Tied to Higher Midlife Cancer Risk,” “Obesity Is Driving Rise in Cancer Among Young People” and “Being Overweight Raises Cancer Risk Twice as Previously Thought.”