Fighting weight gain after breast cancer

| February 22, 2020

Cancer often causes sharp declines in weight, but after a diagnosis of breast cancer, weight gain in some women has been reported.

This is thought to be the consequence of several factors, including the type of treatment women receive, and the impact of this treatment on their lifestyle and habits. Weight gain after a breast cancer diagnosis may not seem the most pressing issue, but it can lead to poorer health outcomes including a higher likelihood of their cancer reoccuring.

In Australia, the only research we have to date on weight gain after breast cancer is from a cohort study of 287 women in the state of Queensland .

Our research team from Western Sydney University and Macquarie University/ICON Cancer Centre were interested in the quantifying the incidence of weight gain after breast cancer, the patterns it can take and the factors which might predict it in patients.

We hope this information will help health care providers offer greater support for the women most at risk of gaining weight during and after their treatment.

Our team has therefore conducted the first national survey of weight after breast cancer in Australia, published in BMC Cancer. We had 309 responses to our survey, most of them sourced from Breast Cancer Network Australia. The average time since diagnosis was 8.2 years, and 82% of women had been diagnosed with Stage 1-3 breast cancer.

The proportion of women who were overweight or obese, with a body mass index (BMI) over 25, rose from just under half at time of diagnosis (48.5%) to around two-thirds (67.3%) at the time of the survey. This included a large increase in the proportion of women who were obese (BMI of 30+) from (17% to 32%. On average, the women surveyed gained 4.5kg of weight after their diagnosis.

Most women (63%) reported gaining weight after breast cancer, with an average increase of 9.07kg. Half of all respondents gained 5 kg or more. Women reported gaining most of the weight within the first two years since diagnosis, and more than half expressed high levels of concern about this increase.

When we compared the rate of weight gain per year with data from the AusDiab study, a large study of more than 11,000 adults aged 25 years and over, we found that, on average, the women surveyed gained 0.48kg per year more than their healthy peers.  Around two thirds (69.8%) of our respondents gained more than the average weight gain for women without breast cancer.

What do we recommend?

Our study revealed worrying levels of weight gain after breast cancer, with around half of our respondents gaining enough weight to potentially have a negative impact on their future health and wellbeing. This may include higher risk of chronic disease such as cardiovascular disease, and possibly a higher risk of tumour recurrence.

Women in our study also reported high levels of concern about their weight. Women with breast cancer often have body image concerns, and weight gain can make this worse. Although we did not look at quality of life in our study, this is an important area for future research.

Our study suggests that there is a window of opportunity within the first 12-18 months after diagnosis to provide additional support for weight management to prevent or limit weight gain among women with breast cancer.  This is consistent with international research that demonstrates that weight gain tends to happen in the first 18 months after diagnosis.

We recommend that all health professionals need to be aware of the risk of weight gain after breast cancer, advise women about this risk, and provide support in the way of referral to a team of health professionals that can assist.

This includes exercise physiologists, as recent recommendations from the Clinical Oncology Society of Australia guidelines recommend that all people with cancer be prescribed exercise as a therapy.

Exercise is an effective treatment for fatigue after breast cancer, and women should receive tailored exercise prescriptions under supervision by an exercise physiologist.

More research on effective interventions for weight gain prevention, including physical activity, diet, behavior change, and social support are required.

Study limitations

Our study inevitably has some limitations. Most of our respondents were sourced from the Breast Cancer Network Australia Review and Survey Group, for example, as this group of women have agreed to be contacted about research on breast cancer.

While this allows researchers to contact women who are engaged in the research process and simultaneously protects other women from frequent research requests, it does limit the validity of our findings as the BCNA Review and Survey Group represents only 2% of all BCNA members.

Weight was self-reported in our study, and there is the possibility it was underestimated or otherwise inaccurate. However, using a self-report approach allowed us to receive responses from across Australia.

We are conducting further analyses of our data to determine the factors that might predict weight gain among our respondents. Receiving chemotherapy, and being younger and premenopausal at diagnosis has been associated with more weight gain in other studies.

Our findings will help health professionals to tailor their management for women who need additional support.  We hope that together we can support women with breast cancer to be as healthy as they can be.

This article was written by Dr Carolyn Ee, GP and senior research fellow at Western Sydney University, and Prof John Boyages, a radiation oncologist at the ICON Cancer Centre.