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Weight Changes
Weight changes, either loss or gain, are common during cancer treatment. There are things you can do to manage changes in your weight.
Weight loss
Many people with cancer lose weight. But losing too much weight can make it harder for you to handle the side effects of treatment and can put you more at risk for infection and fatigue.
What causes weight loss?
There are a number of possible causes for weight loss, such as:
- Eating less due to nausea or loss of appetite
- Diarrhea
- Vomiting
- Dehydration (not taking in enough fluid to make up for fluid that’s lost)
- Increase in the body's calorie needs from cancer and cancer treatment
Symptoms of weight loss
- Losing weight without trying
- Fatigue
- Weakness and less strength to do usual tasks
- Feeling very thirsty
- Dizziness
- Clothes or rings that become too loose
If you have lost a lot of weight and are having trouble eating enough to keep your weight up, you might have something called cancer cachexia.
Managing weight loss
Your cancer care team will talk with you about why you are losing weight. This will help them decide the best ways to help you maintain or gain back the weight you have lost.
- Drink enough water and other liquids.
- If you have diarrhea, drink at least 1 cup of liquid after each loose bowel movement.
- Drink liquids between, not during, meals. This will help prevent your stomach getting full too quickly.
- If you have nausea or pain that keeps you from eating and drinking, talk to your cancer care team about medicines that might help manage those symptoms.
- Eat more often. Try having several small meals or snacks throughout the day, rather than 3 larger meals
- Choose snacks that are high in calories and protein such as nuts, trail mix, dried fruit, granola, peanut butter, hard-boiled eggs, or cheese.
- Drink smoothies, milkshakes, and nutritional supplements or bars to put more calories and protein in your diet.
- Eat your favorite food any time of the day: Eat breakfast foods for dinner; dinner foods for lunch
- Try some tips on getting more calories and protein and include these in meals and snacks throughout the day.
Ask about working with a registered dietitian nutritionist (RDN) or registered dietitian (RD) to come up with a plan that works for you.
Talking with your cancer care team about weight loss
Weight loss can be a sign of a more serious problem. Tell your cancer care team if you:
- Lose more than 3 pounds in a week (or in less than a week). Quick weight loss can be a sign of dehydration, which can be serious.
- Lose more than 5% of your body weight in a year without trying.
- Feel weak, very tired, or dizzy.
- Are not able to do usual activities.
- Are not able to eat or drink as much as usual.
Weight gain
Some people with cancer gain weight during and after treatment. This happens most in people with breast, prostate, or ovarian cancer who are taking certain medicines, getting hormone therapy, or certain kinds of chemotherapy.
Cancer treatment can cause weight gain
Cancer treatments such as chemotherapy, steroid treatment, and hormone treatments can lead to weight gain in different ways.
- It can cause fatigue, making it harder to be active.
- It can cause nausea that might improve when food is eaten.
- It can trigger food cravings.
- It can lower your metabolism so that you burn fewer calories, which can make you gain weight.
- It can cause menopause, which also slows down your metabolism.
Steroid medicines are used to treat some kinds of cancer or to treat side effects of cancer or cancer treatment. Steroids can:
- Increase your appetite, making you eat more.
- Decrease muscle mass, called wasting.
- Increase fat tissue in the belly, neck, face, or other areas if used for a while.
Hormone therapy is used to treat certain cancers, including breast, prostate, testicular, and uterine cancers.
- Hormone therapy can decrease the amount of certain hormones in your body, such as estrogen, progesterone, or testosterone.
- It can increase fat, decrease muscle, and make it harder to burn calories.
Swelling from cancer and treatment
Some types of cancer and cancer treatment can make the body hold on to extra fluid, causing edema (swelling). This can cause weight gain.
- Lymphedema is a build-up of fluid in the fatty tissues just under your skin. This can develop because of the cancer or cancer treatments. Lymphedema happens most often in arms, legs, breast, chest, or shoulder.
- Ascites is fluid buildup in the belly (abdomen) because of pressure from tumors. It can cause the belly to be swollen and hard.
- Swelling in other parts of the body, such as feet and lower legs.
Symptoms of weight gain
- Increase in weight of at least 5 pounds or more in a week or less
- Swollen ankles
- Shortness of breath
- Feeling puffy or bloated
- Tight shoes, clothes, or rings
Managing weight gain
Talk with your cancer care team about what is causing your weight gain. Knowing what is causing you to gain weight will help you know what to do to manage it.
- Ask if you need to limit fluid if your ankles are swollen. If you have swelling in your abdomen (belly), limiting fluids may not help and you should call your cancer care team.
- Ask about working with a with a registered dietitian nutritionist (RDN) or registered dietitian (RD) to help you come up with a healthy eating plan.
- Choose healthier, lower calorie foods.
- Cut back on drinks sweetened with sugar. Drink more water and non-sweetened drinks.
- Limit food portions especially with high-calorie foods.
- Read food labels to become more aware of portion sizes and calories. Be aware that “low-fat” or “non-fat” doesn’t always mean “low-calorie.”
- Limit your salt intake if your cancer care team tells you to.
- Be as active as you can – after checking with your cancer care team. Talk with your team about working with a physical therapist to help you become more active.
If you have been told it would be good for you to lose weight, make sure that you work with your cancer care team to develop a plan for healthy weight loss. Losing weight quickly and not eating enough protein and calories can make it harder for you to cope with and recover from treatment.
Talking with your cancer care team about weight gain
Notify your cancer care team if you:
- Gain more than 5 pounds in a week
- Feel short of breath
- Feel dizzy or confused
- Written by
- References
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
American Society of Clinical Oncology. Weight Gain. Accessed at cancer.net. Content is no longer available.
Baker Rogers J, Syed K, Minteer JF. Cachexia. [Updated 2022 Jan 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK470208/#_NBK470208_pubdet_
Cope D. Nutrition issues. In: Brant JM, ed. Core Curriculum for Oncology Nursing. Elsevier; 2020: 390-400.
National Cancer Institute. Nutrition in Cancer Care (PDQ) – Health Professional Version. Cancer.gov. Accessed at https://www.cancer.gov/about-cancer/treatment/side-effects/appetite-loss/nutrition-hp-pdq#_18_toc on February 6, 2024.
National Comprehensive Cancer Network (NCCN). Clinical practice guidelines in oncology: Palliative care. Version 2.2023. Accessed at https://www.nccn.org on February 6, 2024.
Last Revised: June 26, 2024
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
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