Body weight, exercise and their relationship to something as complex as breast cancer may seem too daunting to consider, but a fairly large body of evidence suggests that these factors absolutely relate to risk and outcome.

This week’s post is the first in a three-part series sharing insights and highlights from “Cancer Survivorship Lifestyle Guidelines: Time for Action”, a session I attended in October 2017 at the Academy of Nutrition and Dietetics Food and Nutrition Conference and Exhibition.

With a strong nod to reducing recurrence risk, this session focused on two specific areas of research; nutrition and physical activity, with the often-cited 2012 ACS Guidelines Nutrition and Physical Activity serving as the starting point. (1)

This two-part session presented research supporting up-to-the-minute recommendations and highlighted the challenges in sharing those recommendations with the cancer community and beyond.

  • Part I Achieving and maintaining a healthy weight/physical activity presented by Dr. Jennifer Ligibel, Dana Farber Cancer Institute breast oncologist, and
  • Part II Diet, nutrition, functional foods, and supplements presented by Dr. Wendy Demark-Wahnefried, RD, chair of nutrition sciences and board member/advisory panel for ASCO Energy Balance Working Group and National Comprehensive Cancer Network, Survivorship Panel 

The program was so content-rich that three posts are necessary to share it all; let’s begin with an overview and background of obesity and physical activity.

Where’s the Evidence?

An overview of the data suggests that obesity and inactivity are linked to a higher risk of recurrence and mortality in early stage, potentially curable disease.

Although Dr. Ligibel is a breast oncologist, she presented research supporting this connection for a number of cancers, including colorectal and prostate.

Because I work with the breast cancer community I’ll focus on outcomes for that population, but please keep in mind that regardless of the type of cancer you want to reduce risk for or have been diagnosed with, this information applies.

An opening question posed by Dr. Ligibel: “What happens when we take someone diagnosed who is overweight or obese and not exercising, and we help them lose weight and exercise more – how do those interventions affect outcomes and quality of life?”

Obesity and Breast Cancer Outcomes

Observational Evidence

Weight and exercise and their relationship to something as complex as breast cancer may seem too daunting to consider, but a fairly large body of evidence suggests that these factors absolutely relate to risk and outcome. A 2003 paper in the New England Journal of Medicine looking at the relationship of body weight and malignancy found that the heaviest participants were at greatest risk of developing multiple malignancies. (2)

Studies linking body weight at time of diagnosis to risk of recurrence and mortality is best studied in breast cancer, with over 100 studies looking at the relationship of a woman’s weight at time of diagnosis of breast cancer and risk of breast cancer mortality.

A meta-analysis summarized 82 reports of >162,000 women with early cancer. Women who are obese when diagnosed with breast cancer have a 35% higher risk of dying from breast cancer as compared to women of normal body weight. The relationship of obesity and poor outcomes in early cancer was seen in both younger and older women; suggesting “a prognostic factor for a large group of breast cancer patients.” (3)


Prospective cohort studies don’t include a lot of information about the treatment women received, yet we do have current studies indicating how chemotherapy treatment that is both different and the same impact outcomes.

Dr. Ligibel shared that obesity is a disease that can influence oncologists’ prescribing of chemotherapy. For example, a doctor may not prescribe as aggressive a chemotherapy regimen for an obese versus a leaner patient.

Chemotherapy is prescribed based on body surface area, indicating that heavier women would require an increased dose. The oncologist may “cap the dose”, or use ideal versus actual body weight, a practice that can influence outcomes. If not enough chemo is used, obese patients may do poorly, not because of their weight, but because of the treatment they received. (4)

A study from the late 1990’s that tested then common chemo drugs still used today, in concert with a more recent study looking at BMI (body mass index) and outcomes in node-positive breast cancer indicate that women with a BMI in the normal range have better outcomes, lower risk of recurrence, and better overall survival compared to women who were overweight or obese.

BMI was shown to be an independent predictor of recurrence and overall mortality; each unit increase in BMI corresponded to a 1.5% increase in the risk of recurrence, for example: BMI 22-27 = 8% increase, 22-32 17% increase, despite the fact that all women received identical chemotherapy treatment. (5)

Physical Activity, Cancer Risk and Outcomes

There is a growing body of literature, although at this point not quite as vast as the hundreds of studies on obesity and breast cancer, linking physical activity patterns after diagnosis and the risk of cancer-related and overall mortality, as well as cancer risk and outcomes.

For breast cancer, there is a relatively limited number of studies – yet consistent findings – indicating that engaging in physical activity can lower the risk of cancer-related and overall mortality when compared to women who are inactive.

Inactivity in cancer survivors is common, with only approximately one-third of cancer survivors engaging in regular activity, and a full one-third not engaging in any physical activity at all. Of course, physical activity certainly can be impacted by cancer diagnosis and treatment: studies have indicated that women decrease exercise by an average of one-third after diagnosis. (6)

Intervention – Can It Help?

We know that obesity and inactivity are linked to poorer outcomes at diagnosis and are definite risk factors, yet health professionals can intervene and help to improve prognosis by helping patients exercise more and lose weight.

Dr. Ligibel posed this question, “Can we help change by intervening? What do we really know about weight loss and physical activity interventions in people with cancer?”

We know that health professionals can actually help people at this phase of their lives change behavior, exercise more and lose weight.

Dr. Ligibel asked, “Why would losing weight and exercising more be different for breast cancer patients than any other person?”

Her response, “This is hard for people in general, but there are different aspects that make it easier in some ways – people are very motivated in seeking change. Yet there are also barriers; cancer therapy leaves people tired, gives side effects like neuropathy, and other things that make implementing exercise more difficult.”

  • So what does this accomplish?
  • How does it make people feel when they change their fitness levels?
  • Does this have an impact on long term outcomes, risk of recurrence and overall mortality?

Join me next week as I wrap up the healthy weight and physical activity coverage with exciting outcomes highlighting what current literature shows.

If you’ve been newly diagnosed with breast cancer, do you know which foods are best to include in your breast cancer diet? For a customized nutrition plan, practical tips and education from a qualified nutrition professional and breast cancer survivor, CLICK HERE.

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  1. Summary of the ACS Guidelines on Nutrition and Physical Activity
  2. Overweight, Obesity, and Mortality from Cancer in a Prospectively Studied Cohort of U.S. Adults
  3. Body mass index and survival in women with breast cancer—systematic literature review and meta-analysis of 82 follow-up studies
  4. Randomized trial of dose-dense versus conventionally scheduled and sequential versus concurrent combination chemotherapy as postoperative adjuvant treatment of node-positive primary breast cancer: first report of Intergroup Trial C9741/Cancer and Leukemia Group B Trial 9741.
  5. Body Mass Index, PAM50 Subtype, and Outcomes in Node-Positive Breast Cancer: CALGB 9741 (Alliance).
  6. Changes in Body Fat and Weight After a Breast Cancer Diagnosis: Influence of Demographic, Prognostic, and Lifestyle Factors