'Never Too Late' to Lower Breast Cancer Risk via Weight Loss

Liam Davenport

December 18, 2019

Women in their 50s who experience sustained weight loss over 10 years are at reduced risk for breast cancer in comparison with those whose weight remains stable, US researchers conclude from a large prospective study.

"Our results suggest that even a modest amount of sustained weight loss is associated with lower breast cancer risk for women over 50," commented lead author Lauren Teras, PhD, Epidemiology Research Program, American Cancer Society, Atlanta, Georgia.

The study involved more than 180,000 women aged 50 years or older who were followed up for 18 years.

It found a linear relationship between weight loss and breast cancer risk reduction.

Women who lost up to 4.5 kg (10 lb) had a 13% lower risk for breast cancer than women whose weight remained stable.

The risk for breast cancer was reduced even more among women who lost more weight (by 16% among those who lost up to 9 kg [20 lb], and by 26% in women who lost 9 kg or more).

"These findings may be a strong motivator for the two thirds of American women who are overweight to lose some of that weight," Teras commented in a statement.

"Even if you gain weight after age 50, it is not too late to lower your risk of breast cancer," she said.

The study was published online on December 17 in the Journal of the National Cancer Institute.

It "supports the notion that lowering overall body weight reduces the risk of cancer," commented Stephanie Bernik, MD, chief of breast surgery, Mount Sinai West, New York City, who was not involved in the study.

However, "the exact mechanism of this effect was not identified," suggesting that "perhaps women that lost weight made a conscious effort to live a healthier lifestyle overall, which may have included a healthy diet, more exercise, and less drinking, all of which contribute to a lower risk of cancer."

Bernik urged women to "use this information to motivate them to make lifestyle changes that may ultimately influence longevity."

"In the United States, where obesity is the norm, hopefully studies like this will help women understand the importance of healthy living," she said in a statement.

Study Details

For the study, Teras and colleagues examined data from the Pooling Project of Prospective Studies of Diet and Cancer (DCCP), an international consortium of prospective cohort studies established in 1991 to investigate the link between dietary factors and cancer risk.

The current analysis focused on 10 cohorts from the United States, Australia, and Asia and was restricted to women aged 50 years or older. At least three surveys included body weight and breast cancer incidence data.

A total of 180,885 women were included, of whom 6930 (3.8%) were diagnosed with breast cancer.

Weight change was monitored for 10 years. The study period was divided into two intervals of approximately 5 years; the women were subsequently followed up for a median of 8.3 years.

At the start of the first 5-year interval, the median age was 59 years, and the median body mass index (BMI) was 25.1 kg/m2. At the end of the second interval, the median BMI was 25.6 kg/m2.

During the 10 years during which the women were monitored, 20.3% maintained a stable weight; 21.8% lost weight during the first 5-year interval, and half of these (50%) sustained this weight loss during the second 5-year interval.

In addition, 37.3% of the women gained weight during the first 5-year interval, and the majority (74.1%) sustained this weight gain through the second interval.

The team found that women with sustained weight loss had a lower risk for breast cancer than those whose weight was stable. This relationship was linear and was confined to women who did not use hormone replacement therapy (HT) at the start of breast cancer follow-up.

The researchers say that the stronger association between weight loss and breast cancer risk in non-HT users was "not unexpected."

They explain: "This difference by HT use is likely due to the increase in circulating sex hormones caused by exogenous hormone use, which may overwhelm more moderate changes in hormones due to adipose tissue alone.

"In women not taking HT, the endogenous hormone shift caused by weight loss may be more influential," the authors suggest.

"The importance of this interaction, however, has lessened in recent years due to the drastic decline in the use of postmenopausal hormones, estimated to be down to less than 5% of US women in 2010," they note.

The research was supported by grants from the Breast Cancer Research Foundation and the National Cancer Institute. The authors have disclosed no relevant financial relationships.

J Natil Cancer Inst. Published online December 17, 2019. Abstract

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