Weight Gain

Approved by the Cancer.Net Editorial Board, 03/2021

During cancer treatment, you may find it hard to maintain your weight. Some people lose weight. Others gain weight. Slight increases in weight during cancer treatment are usually not a problem. But if you gain too much weight, it can affect your health.

Weight gain is more common with some cancers and some treatments than others. For instance, more than half of people with breast cancer gain weight during their treatment. Research shows that too much weight gain during treatment is linked to a poorer chance of recovery. Being overweight before treatment begins can also increase the risk of health problems. These include high blood pressure, diabetes, and heart problems.

Talking about your weight with your doctor is important, but it can be hard or stressful for some people. Some people feel ashamed about their weight or weight gain. Some people have even experienced discrimination because of their weight. Weight gain can be a side effect of your cancer treatment. It is important to talk to your health care team if you notice changes in your weight, eating habits, or bloating. This will help them find the best support for you.

What cancer treatments can cause weight gain?

Cancer treatments such as chemotherapy, steroid treatment, and hormone treatments can lead to weight gain in different ways.

Chemotherapy. Chemotherapy uses drugs to destroy cancer cells. Chemotherapy can lead to weight gain by:

  • Causing the body to hold on to excess fluid, called edema.

  • Causing fatigue, making it harder to exercise.

  • Increasing nausea that improves by eating more food.

  • Triggering intense food cravings.

  • Lowering your metabolism. Metabolism is the rate that the body uses energy. When your metabolism is low, you burn less calories, which can make you gain weight.

  • Causing menopause, which also slows down your metabolism.

Steroid medications. Steroids are prescribed during cancer treatment for several reasons. This type of medication can reduce symptoms of inflammation, such as swelling and pain. They can treat nausea. And they can be used as a treatment for cancer itself, such as for multiple myeloma.

A common side effect of steroids is weight gain. Steroids can lead to weight gain by:

  • Increasing your appetite and making you eat more.

  • Decreasing muscle mass, called wasting.

  • Increasing fat tissue in the abdomen, neck, face, or other areas with long-term use.

Hormonal therapy. Hormonal therapy may be used to treat certain cancers, including breast, prostate, testicular, and uterine cancers. This type of medication can decrease the amount of certain hormones, such as estrogen, progesterone, or testosterone. Hormones in the body are used for different functions. Decreases in hormone levels can increase fat, decrease muscle, and make it harder to burn calories.

How can weight gain during cancer treatment be managed? (updated 06/2022)

Many people will gain weight during treatment for cancer. There are a number of reasons why patients may gain weight during cancer treatment. Some people may become less physically active during cancer treatment. Others may receive medications that change their metabolism. This is especially true for people being treated for breast cancer or prostate cancer. Sometimes, medications that contribute to weight gain are given as part of the treatment plan, such as steroids.

Before starting any kind of diet or changing your eating habits, talk with a member of your health care team. You may find it helpful to talk with a registered dietitian (RD). They can provide nutritional guidelines or a customized diet plan.

General suggestions about good nutrition during cancer treatment include:

  • Eat plenty of fruits, vegetables, and whole grains.

  • Limit fat, sugar, and refined flour.

  • Drink plenty of water.

  • Use healthier cooking methods whenever possible.

Regular physical activity can also be helpful during and after cancer treatment. Check with your doctor before starting a new type of exercise or increasing your physical activity.

  • Try different physical activities, such as walking or bicycling, to find one that you enjoy and will do regularly.

  • Explore exercise classes designed for people diagnosed with cancer, either in-person or online.

  • Try strength-building exercises. These can be especially helpful if you have lost muscle.

It is important to talk with your cancer care team regularly about your overall physical and mental health.

Some people have questions about preventing weight gain during cancer treatment. There has not been enough research yet to determine how measures to prevent weight gain during active treatment affect quality of life, treatment side effects, or cancer outcomes. Therefore, ASCO cannot make any specific recommendations for or against weight loss during cancer treatment.

How can weight gain from fluid retention be managed?

Fluid retention or edema is swelling caused by the buildup of fluid in the body. If you have edema, you might feel like your clothes, rings, or shoes are too tight. People with edema can also have less flexibility in their hands, elbows, wrists, fingers, or legs. Swollen arms or legs, especially around the wrists or ankles, are also a sign of edema. The fluid buildup collects under the skin, so your skin might feel puffy or stiff. Pressing on your skin might leave small indentations.

Talk to your health care team about any of these symptoms so they can diagnose and treat edema. Some of the ways edema can be managed include:

  • Medication. Your doctor can prescribe a diuretic to remove excess water.

  • Lower the amount of salt in your diet.

  • Avoid standing for long periods.

  • Elevate your feet as often as possible.

  • Avoid crossing your legs, which restricts blood flow.

  • Weigh yourself at the same time every day to keep track of changes. This can help your health care team see any fluctuations in your weight that might be caused by edema. Bring this log with you to appointments for your health care team to evaluate.

  • Avoid tight clothing and footwear.

  • Ask your health care team if wearing support or compression socks may help.

Questions to ask your health care team

  • Can this cancer or its treatment cause weight gain?

  • Can my cancer treatment cause edema?

  • What are ways I can track my weight during cancer treatment?

  • Who should I tell if I notice changes in my weight?

  • Is there an oncology dietitian and/or other specialists that I can talk with about making food choices and my exercise routine?

  • Are there certain exercises I should avoid due to my diagnosis or its treatment?

  • Who can I talk with if I need help coping with stress or other emotional effects of cancer?

Related Resources

Body Weight and Cancer Risk

Managing Physical Side Effects