MSK breast medical oncologists Neil Iyengar, MD (left) and Sherry Shen, MD study the relationship between diet, exercise, and cancer and have insights to help people manage weight gain during breast cancer treatment.
Advances in breast cancer treatment mean more people than ever are recovering their health. Today, there are nearly 4 million breast cancer survivors in the United States, and that number will continue to grow, thanks to life-saving therapies.
People diagnosed with breast cancer can help their recovery by being aware of a common side effect of breast cancer treatment — weight gain.
“Most people experience weight gain following breast cancer diagnosis,” says breast medical oncologist Sherry Shen, MD, of Memorial Sloan Kettering Cancer Center (MSK). “That can cause anxiety. However, patients should know there are many ways weight gain can be managed, both during and after treatment.”
Dr. Shen conducts research on the complex relationship between the body’s metabolism and cancer, as does her MSK colleague, Dr. Neil Iyengar, MD, who also cares for people with breast cancer as a medical oncologist.
“The treatments we give people for breast cancer are lifesaving and absolutely vital,” explains Dr. Iyengar. “It’s also important that people facing breast cancer understand that breast cancer and its treatments have effects on the body’s metabolism that need to be addressed both to help with cancer treatment and for patients’ long-term health.”
In this article, Drs. Shen and Iyengar share the guidance they give their patients facing breast cancer, including tips for controlling weight, the latest MSK research on the topic, a promising approach using the app Noom, and an analysis of the new GLP-1 agonist weight loss drugs including Ozempic and Wegovy.
Why People With Breast Cancer Often Gain Weight During Treatment
Dr. Iyengar explains that “in order to kill the cancer cells, many of the treatments we use have side effects that change the biology of the body.”
“In chemotherapy for breast cancer, we give steroids and lots of fluids, which can induce weight gain,” says Dr. Shen. “And, due to nausea, many patients alter their eating habits, which can also result in weight gain.”
The doctors point out that some kinds of breast cancer treatment may also put women into menopause. “Chemotherapy can induce a temporary menopause,” says Dr. Iyengar, “which deprives the body of the hormone estrogen and can lead to changes including weight gain.”
Dr. Shen says that “hormone therapy, which is very common for breast cancer, also alters metabolism. Especially for younger patients, this treatment can put them into menopause, which tends to mean more weight gain.”
Both doctors emphasize that despite these side effects, the treatments are crucial. “These therapies can cure breast cancer,” says Dr. Iyengar, “so lifestyle interventions synergize but do not replace standard cancer treatments.”
Who Is Most at Risk of Gaining Weight After a Breast Cancer Diagnosis
Weight gain is particularly common among people with hormone receptor positive breast cancer, who account for nearly 70% of people diagnosed with breast cancer.
Drs. Shen and Iyengar say patients who are most likely to gain weight during breast cancer include:
- People receiving chemotherapy
- Patients receiving hormone therapy
- Younger patients
Dr. Iyengar also points out that “we’re learning more about populations that historically have been understudied. Black and Hispanic breast cancer patients, as well as male patients with breast cancer, appear to be at higher risk of weight gain.”
This is also a concern for patients who are no longer on active treatment or were diagnosed years earlier, a phase often called “survivorship.” Dr. Iyengar says, “We’re now using hormone therapies for up to 10 years, so people will transition into survivorship while they’re still on hormone therapy.”
He stresses that it’s important that people in this phase “maintain good general health, and monitor their cholesterol and cardiovascular health, which is easier if good eating and exercise patterns are set up early in their treatment.”
The Consequences of Weight Gain During Breast Cancer Treatment
Dr. Shen and Dr. Iyengar recognize the unique stresses of cancer. “We want people to be mindful of what they eat and their patterns of eating.” says Dr. Iyengar.
One aspect of that mindfulness is recognizing that serious weight gain during breast cancer can have consequences for a person’s recovery and overall health.
Dr. Iyengar says that “people who have been treated for breast cancer are more than two times as likely than people who have not been treated for breast cancer to develop cardiovascular disease, diabetes, and other metabolic disorders, including obesity.”
In fact, says Dr. Iyengar, “the leading cause of death among patients with early-stage breast cancer is not breast cancer itself, but rather cardiovascular disease.”
“We know from research that breast cancer outcomes get worse with weight gain that is more than 5% of a person’s total body weight at the time of diagnosis,” says Dr. Shen. “So trying to control weight during breast cancer treatment is important in many ways, including lowering the chance of cancer recurrence.”
How to Control Weight Gain During Breast Cancer Treatment
Nutrition and Food
Dr. Shen and Dr. Iyengar say there is no “one size fits all” approach to controlling weight during cancer treatment, because individuals have different needs and varied approaches to food.
With her patients, Dr. Shen stresses a few key concepts.
- A plant-forward diet “I talk to patients about consuming a plant-forward diet,” she says. “That’s not saying people need to convert to being vegetarians or vegans. But they should prioritize plant-based whole foods, including fruits and vegetables, whole grains and eat less red meat and processed meat.” For protein, people should “focus on seafood and plant-based sources,” she says.
- Dietary fiber Another key, she says, “is getting enough dietary fiber, which has been shown to reduce the risk of breast cancer recurrence.” She says it’s especially important for cancer patients to also stay hydrated with a healthy water intake, as high dietary fiber without adequate hydration can lead to constipation.
- Calories For weight loss, she stresses knowing both how many calories a person is consuming and trying to focus on the quality of the calories. Consuming fewer calories leads to weight loss,” she says, “but the quality of those calories is important too.”
- Sugar Dr. Shen stresses to her patients to limit added sugars and she echoes the recommendations of MSK nutritionists, who urge people to consider healthier options when possible, such as honey or maple syrup, for sweetening rather than refined sugar. “People also need to be aware of the hidden added sugars in sodas and similar sweetened beverages,” says Dr. Shen.
Physical Activity
“Research shows that physical exercise can really help both with weight loss as well as improving breast cancer outcomes,” says Dr. Shen. “It can also help people who contend with body image issues as a result of breast cancer.”
Her advice to patients, based on extensive research at MSK and elsewhere is:
- At least 150 minutes per week of moderate exercise — about the pace of a brisk walk
- Or at least 75 minutes a week of vigorous activity that gets the heart rate up, such as playing a sport, running, or swimming
The Individual Angle
Dr. Iyengar says that research at MSK is revealing much more about “why something that works for one person doesn’t work for another. We’re learning how to tailor recommendations for each individual.”
That’s one of the focuses of the MSK Healthy Living program, which was founded by Dr. Iyengar. “We produce a plan that’s specific to the needs of each breast cancer patient in the program,” explains Dr. Iyengar, “so we can maximize their potential to live their best life during and after cancer.”
In addition to nutrition and exercise, the program also produces a personal plan to address a wide range of needs specific to each patient, from sleep and sexual health to mental well-being, financial health, and more.
MSK Research To Control Weight Gain During Breast Cancer Treatment
MSK is also pioneering new ways to help people control their weight during breast cancer treatment through rigorous research and clinical trials.
Pilot project with Noom mobile app
A pilot project led by Dr. Shen used the popular mobile app Noom to investigate if lifestyle interventions could help breast cancer patients prevent or even reverse weight gain.
The app was provided to 31 patients with early-stage cancer (Stage 1 to 3) who were in the overweight or obese range and who had completed breast cancer treatment at least six months earlier.
“Noom is meant to help change a person’s thought process and habits so that they adopt overall eating patterns that are more healthy,” says Dr. Shen. “In the app, people can access articles about healthy eating and exercise, talk with support groups and coaches, log the food they eat each day, as well as their weight and physical activity, and they don’t need to travel to a clinic to do it or check in repeatedly with a counselor, which many people find inconvenient.”
After half a year with the program, “people lost an average of 5.6% of their body weight, which is quite high,” says Dr. Shen. “Research shows that amount of weight loss can improve breast cancer outcomes and makes people healthier. We also saw a noticeable improvement in people’s body image.”
Dr. Iyengar says, “One really exciting aspect of this trial is that it can be scaled up, since it’s done on an app, which is much more convenient for people than coming for clinic visits. That also means its more sustainable over a longer period of time.”
Plant Based Meals and Exercise
A separate MSK trial tried a different approach and delivered plant-based meals directly to breast cancer patients alongside personal exercise training. “This was a more time-intensive intervention,” says Dr. Iyengar, “because it included personalized exercise and nutrition prescriptions, meal delivery, and virtually supervised exercise sessions, but the results were very encouraging.”
The average weight loss among participants was 14%, while average gain in lean muscle mass was 7%.
Weight Loss Drugs Such as Ozempic and Wegovy
Dr. Shen and Dr. Iyengar also conducted an analysis of breast cancer patients who took the weight-loss drugs often grouped together as GLP-1 agonists that include Ozempic and Wegovy.
“These patients were taking the drugs because of diabetes, not for weight loss,” explains Dr. Shen. “But they averaged around 5% weight loss over the period we analyzed, which is very encouraging for overall health and breast cancer outcomes.”
Dr. Shen emphasizes that “this was only 75 patients, and much larger, controlled studies need to be done.” However, she and Dr. Iyengar believe this analysis adds to a growing body of evidence that these medications can help some people who face serious weight gain during cancer treatment.
The bottom line, says Dr. Iyengar, “is that we know diet and exercise can help people control weight during breast cancer treatment. And we have a range of interventions to help. With the right support, people with breast cancer can be empowered to play an important role in their own recovery and set themselves up for healthier living in the future.”