June 25, 2012
Exercise Reduces Breast Cancer Risk, Weight Gain Negates The Effect
Lawrence LeBlond for redOrbit.com
A new US study has found that women who maintain physical activity -- even mild exercise -- before or after menopause may reduce their overall risk of breast cancer, but substantial weight gain may cancel out these benefits.
Previous studies have shown that physical activity can reduce the risk of breast cancer, but many questions also followed. How often should a woman exercise, and for how long? And how intense should that exercise be? Also, does exercise reduce the risk for women of all body types?
That´s where Lauren McCullough, University of North Carolina Gillings School of Global Public Health in Chapel Hill, came in. She and colleagues wanted to tackle these questions head-on and try to provide a better understanding of the results.
In her study, “Fat or Fit: The Joint Effects of PA, Weight Gain and Body Size on Breast Cancer Risk,” McCullough and her team looked for a link between recreational physical activity, done at different points in life, and the risk of developing breast cancer.
The study, published early in the online edition of the journal CANCER, included more than 3,000 women (1,504 with breast cancer and 1,555 without) from 20 to 98 years old who took part in the Long Island Breast Cancer Study Project -- a multipart study to investigate whether environmental factors were responsible for breast cancer. That study began in 1993.
Some of the key findings in the study were that women who exercised during their reproductive years or during menopause had a reduced risk of breast cancer; the greatest effect was in women who exercised 10 to 19 hours per week, reducing the risk of breast cancer by about 30 percent. Also, all levels of exercise were linked to a reduction in risk of the most common breast cancers.
The study, however, found that women who gained a substantial amount of weight, especially after menopause, had an increased risk of breast cancer, suggesting that weight gain negates the beneficial effect of exercise.
The team did not examine the underlying reasons for the effect of exercise on breast cancer risk, but suggest it may have something to do with controlling energy balance and obesity, that leads to reduced insulin resistance and inflammation.
“The observation of a reduced risk of breast cancer for women who engaged in exercise after menopause is particularly encouraging given the late age of onset for breast cancer,” said McCullough. “Collectively, these results suggest that women can still reduce their breast cancer risk later in life by maintaining their weight and engaging in moderate amounts of activity.”