Weight loss after menopause is linked to reduced risk of breast cancer

(Reuters Health) – A large American study suggests that older women who lose weight may have a lower risk of developing invasive breast cancer than women who maintain or gain weight.

Although obesity has long been associated with an increased risk of breast cancer, previous research has yielded a mixed picture of the potential for weight loss to help reduce this risk. For this study, researchers evaluated weight and height in order to calculate the body mass index (BMI) of more than 61,000 women twice to three years apart.

The researchers then followed the women for an additional 11.4 years on average. During this period, 3,061 women developed invasive breast cancer.

Compared to women whose weight was stable in the first three years of the study, women who lost at least 5% of their body weight in those first three years were 12% less likely to develop cancer. breast during the next decade or so.

"Our findings are consistent with the fact that a woman can reduce her risk of cancer even if she retains an excess weight or is obese after losing weight because almost none of the women in our current cohort analysis n & # 39; 39, lost enough weight to reach a normal weight, "said the manager. Dr. Rowan Chlebowski, author of the study, National Medical Center of Hope City in Duarte, California.

"This should be an encouraging result for women because moderate and lasting weight loss can be achieved by many, while a sufficient weight loss to return to a category of non-obese or overweight people is quite difficult" said Chlebowski by email.

All women participating in the study were postmenopausal, when menstruation stops and the production of estrogen hormone decreases. After menopause, the main source of estrogen in women is adipose tissue; overweight or obesity can increase the risk of cancer because estrogen can promote tumor growth.

"Overweight or obese women are likely to have an increased risk of breast cancer in postmenopausal women due to an increase in hormone levels associated with fat cells," said Dr. Daniel Schauer of the University of California College of Medicine. Cincinnati, who did not participate in the study.

"These hormones, particularly estrogen, can promote the development of breast cancer in postmenopausal women," Schauer told Reuters Health via email. "Losing weight decreases the levels of hormones in circulation."

Of the approximately 41,000 women in the study who had a stable weight in the first three years, participants had an average BMI of 26.7, which is considered excess weight.

The 12,000 women who gained weight during the study also started with an average BMI of 26.7.

Women who lost weight started heavier.

The approximately 3,300 women who lost weight inadvertently started with a BMI of 27.9 and half of them lost more than 17 pounds. Women who have lost weight intentionally started with an average BMI of 29.9, a little less than the BMI threshold of 30 to be considered obese, and half of them lost more than 20 pounds.

A weight gain of 5% or more was not associated with an increased risk of breast cancer, the researchers reported in the journal Cancer. But this weight gain was associated with a 54% higher "triple negative" breast cancer risk, a type of cancer that is aggressive and difficult to treat.

The study was not a controlled experiment designed to prove whether weight change over time could have a direct impact on breast cancer risk in women.

Researchers measured women's weights only twice, at the beginning of the study and again three years later, and any changes in women's weight reported subsequently were not verified by medical exams.

For most people, weight increases over time, said Dr. Graham Colditz of the University of Washington School of Medicine in St. Louis, who did not participate in the study.

"The first realistic goal is to work to stop winning. This has health benefits even in the case of being overweight, "Colditz said by e-mail.

"After that, losing weight in a sensible and slow way is a good goal," added Colditz. "Five to ten pounds is a good start that is more easily maintained over time."

SOURCE: bit.ly/2AreUsz Cancer, online October 8, 2018.