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Cancer and Your Weight

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When you have cancer, you may experience a lot of changes to your body. This can seem scary and overwhelming. Know that this happens to many people with cancer. Your healthcare team is here to help you through these changes.

Many people lose or gain weight when they have cancer. Sometimes the cancer causes the weight change. Sometimes it’s the cancer treatment, such as chemotherapy or radiation therapy, that causes side effects that affect your weight.

Here’s some more information on why weight changes can happen when you have cancer.


Cancer and weight loss

Weight loss during cancer is common. Sometimes, weight loss is the first symptom people notice when they have cancer. Cachexia refers to weight loss that involves increased metabolism, loss of muscle, fatigue, and loss of appetite. Many people with cancer have cachexia.

Possible causes of weight loss in people with cancer

Weight loss may be caused by the cancer itself. Or it may be caused by side effects of cancer treatment.

Weight loss may be related to:

  • Metabolism changes. Your body may use more calories because of the cancer.

  • Nausea, vomiting, or diarrhea

  • Taste changes

  • Mouth sores

  • Trouble chewing or swallowing

  • Pain

  • Dehydration


Cancer and weight gain

Sometimes, people with cancer can gain weight. It is more common with certain types of cancer, such as breast, prostate, and ovarian cancer. It’s also more common with certain treatments.

Possible causes of weight gain in people with cancer

Weight gain may be caused by the cancer itself. Or it may be caused by side effects of your cancer treatment.

Weight gain may be related to:

  • Edema (swelling)

  • Being less active

  • Lower metabolism

  • Steroid medicines, which can increase your appetite

  • Hormone therapy, which can increase fat and decrease muscle

  • Eating more to keep nausea or stress under control


How to deal with weight changes

Let your healthcare team know if you experience weight changes. They can help find the cause and offer suggestions. They may also refer you to a dietitian or nutritionist. You may not be able to completely control your weight when you’re being treated for cancer. But there are things you can do that can help.

If you’re dealing with weight loss:

  • Eat nutrient-dense foods. Choosing foods that are high in calories and nutrients is key to maintaining weight during cancer treatment. Eat protein-rich foods like lean meats, poultry, fish, eggs, and legumes. Opt for healthy fats from sources like avocados, nuts, and olive oil. Incorporate whole grains, fruits, and vegetables to get the vitamins, minerals, and fiber you need.

  • Switch up how often you eat—and how much. Eating smaller, more frequent meals throughout the day can help you get more calories. Aim for 5 to 6 small meals instead of 3 large ones.

  • Add extra calories to your day. Choose healthy options such as cheese, yogurt, nuts, and seeds. Fortify foods with protein and healthy fats to increase the caloric content. Consider using protein or energy supplements recommended by your healthcare team.

  • Try some anti-nausea strategies. Nausea can ruin your appetite. To manage it, try eating smaller, bland meals and avoiding strong odors. Ginger, either in tea or a capsule, has shown promise in reducing nausea. Talk with your provider about anti-nausea medicines.

  • Stay hydrated. This is important, even if drinking large amounts of fluids is tough. Sip water throughout the day. You can also have hydrating foods like soups, smoothies, and fruits with high water content.

Try these strategies if you’re experiencing weight gain:

  • Eat healthy. Focus on balanced meals with plenty of fruits, veggies, and whole grains. Try to avoid sugary or high-fat foods. Eating mindfully and having smaller portions can help keep your weight in check, too.

  • Stay active. Try light movement like walking or yoga to help maintain muscle mass and manage weight. You may feel too tired to be active, but any little bit helps. Talk with your healthcare team before adding more movement to your day.

Going through cancer and its side effects is difficult. It’s certainly tough to see changes in your body caused by cancer. But remember that your healthcare team is there to support you through the process, including any weight changes you may experience.

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© 2000-2025 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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