How to Avoid Weight Gain After Breast Cancer

A healthy weight can be a worthy—and important—goal for breast cancer survivors. Here’s how to achieve and maintain it.

There’s a reason that “at least you have your health” is a cliché—and if you’ve faced a serious health threat like breast cancer, the words may ring even truer for you than for other people. But just because you’ve received a clean bill of health doesn’t mean life will automatically go back to the way it was pre-cancer. It’s time to learn how to take care of your newly cancer-free body.

According to American Cancer Society guidelines for survivors, living a healthy lifestyle—which includes making smart dietary choices and being active—may be essential to helping prevent recurrence. And that means it’s crucial to address one of the potential side effects of cancer treatment that often doesn’t get much attention: weight gain.

Breast cancer patients who’ve undergone chemotherapy are about two times more likely to gain 11 or more pounds within five years post-treatment than are women who are cancer-free, according to a study in Cancer Epidemiology, Biomarkers & Prevention. And a Canadian study found that women gained 4 to 13 pounds in the first year after being diagnosed.

If you’ve been treated for breast cancer, you likely already understand why patients may be vulnerable to weight gain. Chemotherapy may interfere with your metabolism or throw you into temporary menopause. Fatigue could sap your motivation to stay active. And no matter how much of a warrior you become in your breast cancer fight, there’s no denying the psychological burden that might lead to emotional eating.

How weight affects breast cancer risk

The number on the scale is a big factor in any breast cancer discussion. Obesity is often linked to increased risk of conditions such as type 2 diabetes or heart disease, but excess weight has also been shown as a risk factor for developing breast cancer specifically—and as a characteristic that affects your long-term survival.

“With breast cancer risk, it’s the actual fat tissue we have to worry about,” says Cheryl Rock, PhD, a professor of family medicine and public health at the University of California, San Diego who has led research on breast cancer survivors. Excess fat may contain higher levels of estrogen, she says, which could stimulate tumor growth. It also has increased levels of other hormones and inflammatory molecules that may be associated with breast cancer.

A recent analysis of 82 studies involving more than 200,000 breast cancer patients found that premenopausal women who had obesity at the time of diagnosis had a 75% greater chance of dying from breast cancer and other causes compared with women with a normal body-mass index (BMI). (It’s a 34% increase for postmenopausal women.) And the risk went up for every 11 pounds a woman gained more than a year after diagnosis.

That means that beating the disease—as big a triumph as it is—may not be a guarantee of long-term health. “Having overweight may increase the risk of breast cancer recurrence,” explains Colleen Doyle, MS, RD, managing director of nutrition and physical activity for the American Cancer Society. “You may see your risk go up from gaining just 5 to 10% of your body weight.”

Achieving and maintaining a healthy weight

Admittedly, getting through breast cancer treatment is plenty challenging unto itself. Now you have to think about reaching a healthy weight, too? Just remember that the effort can pay off in major ways, Doyle says. Losing extra pounds might not only protect you from cancer recurrence; it could improve other aspects of your wellbeing. Progressing toward a healthier weight also may build your confidence in setting and working toward new goals—a potential boon for your mental recovery.

If losing weight sounds like a daunting addition to your recovery to-do list, Doyle advises making the journey as easy on yourself as possible. Start with small changes that help you feel in charge of your health again, and celebrate your everyday victories. “When you were going through treatment, there were so many things going on in your life that you couldn’t control,” she says. “But having the opportunity to take back control of your life and positively affect your health will be a huge step forward.”

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This article was reviewed for accuracy in September 2021 by Michelle I. Cardel, PhD, MS, RD, WW's director of global clinical research and nutrition. The WW Science Team is a dedicated group of experts who ensure all our solutions are rooted in the best possible research.