Weight Changes

Weight changes, either loss or gain, are common during cancer treatment.

Weight loss

Quick weight loss is often a sign of dehydration, which can be serious. Weight loss of more than 3 pounds in a week should be reported to your cancer team. There are a number of causes for weight loss, including:

What to look for

  • Weight loss of 3 pounds or more in a week or less
  • Weight loss continues without trying
  • Dry skin
  • Fatigue, weakness
  • Feeling very thirsty
  • Dizziness
  • Clothes or rings are too big

If you want to try to stop losing weight 

  • Be sure to drink enough water and other liquids. Drink liquids between meals not during, so you won’t fill up.
  • 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 adding high-calorie foods such as whipped cream, sour cream, cream cheese, butter, or gravy to avoid further weight loss.
  • Ask about meeting with a dietitian.

Weight gain 

Some people find they don’t lose weight during treatment. They may even gain weight. This is particularly true for people with breast, prostate, or ovarian cancer who are taking certain medicines or getting hormone therapy or chemotherapy.

Many women with breast cancer gain weight during treatment. Because of this, many of the recommendations for breast cancer patients include a reduced-calorie diet much like those suggested for patients after cancer treatment has been completed. If you have any questions, talk to your cancer care team about the best diet for you. Some people find it helps their nausea to have something in their stomachs, so they eat more. Others eat more when they’re stressed or worried.

If you notice you’re gaining weight, tell your cancer care team so you can find out what may be causing this change. Sometimes you gain weight because certain cancer-fighting drugs cause your body to hold on to extra fluid. If this is the case, your doctor may ask you to talk with a registered dietitian for help with limiting the amount of salt you eat. This is important because salt might cause your body to hold extra water.

An increase in weight over time might also suggest a serious health condition, such as diabetes or high blood pressure. You may be able to tell if you gain or lose weight in a week by the way you feel or the way your clothes fit, or you can weigh yourself on a scale every few days.

What to look for

  • Weight gain of 5 pounds or more in a week or less
  • Swollen ankles
  • Shortness of breath
  • Feeling puffy or bloated
  • Tight shoes, clothes, or rings

If you want to try to stop gaining weight

  • Ask if you need to limit fluid if your ankles are swollen.
  • Choose healthier, lower calorie foods.
  • Cut back on sugar-sweetened beverages.
  • Limit your salt intake.
  • 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.”
  • Try to walk daily if you can and if it’s OK with your doctor. Talk with your cancer care team about referral to a physical therapist to help you safely increase activity levels.
  • Ask about meeting with a dietitian.

What caregivers can do

  • Weigh the patient at the same time every day and write it down along with the date. A good time is in the morning before eating or drinking.
  • Talk to the cancer team if the patient’s weight loss or weight gain concerns you.
  • Watch the patient for other symptoms.

Call the cancer team if the patient:

  • Loses or gains more than 3 pounds in a week
  • Has shortness of breath
  • Feels dizzy or becomes confused

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 journalists, editors, and translators with extensive experience in medical writing.

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Last Medical Review: November 2, 2018 Last Revised: July 30, 2019

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