Weight Changes, Appetite Loss, and Cancer
A plain-language guide to appetite loss, weight loss, weight gain, and malnutrition during cancer treatment, with practical eating tips, based on National Cancer Institute resources.
Source: National Cancer Institute · NCI reviewed 2024-10-15 · Verified 2026-07-02
The 30-second version
Cancer and its treatment can change your appetite and weight—some people lose weight, others gain it, and some develop malnutrition. Appetite loss often leads to eating less than your body needs. Small frequent meals, high-protein and high-calorie foods, and working with a registered dietitian can help you stay strong.
Key takeaways
- Appetite loss and weight loss are common side effects of cancer and its treatments.
- Some people gain weight during treatment, often with ovarian, breast, or prostate cancer, or from steroids and hormone therapy.
- Eating small meals every 2 to 3 hours and choosing high-protein, high-calorie foods can help with appetite loss.
- Malnutrition is when your body doesn't get enough energy, protein, vitamins, and minerals—it can be serious.
- A registered dietitian can create a nutrition plan tailored to you.
- Report weight loss of more than 3 to 5 pounds in a week to your doctor.
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Cancer and cancer treatments can change your appetite and your weight. Appetite loss and weight loss are common, but some people gain weight instead. And weight loss can lead to malnutrition, when your body doesn't get enough nutrients.
Whatever direction your weight goes, tell your team. A registered dietitian can help you and your family manage these changes with a plan that fits you.
Appetite loss and weight loss
Anyone with cancer might lose their appetite and lose weight, but it's more likely with head and neck, lung, pancreatic, or liver cancer, or cancer in the upper digestive system. Appetite loss often leads to eating less than your body needs, which leads to weight loss.
Many side effects make eating harder, including nausea and vomiting, diarrhea, constipation, feeling full quickly, painful swallowing, mouth sores, dry mouth, and taste changes. Anxiety, pain, depression, and fatigue can also reduce appetite.
Ways to manage appetite loss:
- Eat foods high in protein and calories, and eat high-protein foods first when your appetite is strongest.
- Eat small meals every 2 to 3 hours—about 5 or 6 meals a day—and set an alarm if you forget.
- Eat within an hour of waking, and have a bedtime snack.
- Drink milkshakes, smoothies, juices, or soups if you don't feel like eating solid foods; use whole milk or yogurt to add calories.
- Sip nutrition supplement drinks like Ensure or Boost between meals.
- Add cheese, creamy sauces, beans, or leftover meat to boost calories and protein.
- Make eating pleasant—candles, music, and eating with loved ones can help.
If you can't keep your appetite up, ask your doctor about appetite stimulants, which are medicines that increase appetite.
Weight gain
Although many people lose weight, you may gain weight during treatment—more commonly with ovarian, breast, or prostate cancer. Small weight changes are normal, but tell your doctor about sudden gain (like 5 pounds in a week) or gain that doesn't stop.
Causes of weight gain include:
- Fluid retention, from the tumor or fluid buildup.
- Increased appetite, from the cancer, treatment, or medicines.
- Metabolic changes, since hormone therapy can slow your metabolism.
- Medications, especially steroids, which increase appetite and can cause the body to hold onto water.
- Decreased activity, when fatigue and pain make it hard to move.
To manage weight gain, choose high-fiber foods, lean proteins, and low-fat dairy; limit fat, salt, sugary drinks, and alcohol; eat slowly and use smaller plates; and stay as active as you can. If steroids cause swelling, limiting high-sodium foods can help.
Malnutrition
Malnutrition is when your body doesn't get enough energy, protein, vitamins, and minerals. It can be caused by the cancer, the side effects of treatment, or both. Decreased appetite is a main cause in people with cancer, and problems with swallowing, digestion, and absorption can add to it.
Why it matters: malnutrition can make you weak and tired, make it harder to fight infection or finish treatment, lower your quality of life, and even become life-threatening.
Your team may use nutrition screenings to catch eating problems early. To help prevent malnutrition, eat high-calorie and high-protein foods, use supplement drinks, eat small meals every 2 to 3 hours, and report appetite or weight problems to your doctor right away—including weight loss of more than 3 to 5 pounds in one week. If eating stays very hard, your doctor or dietitian may suggest tube feeding or IV nutrition.
Getting support
Family and friends can help with meal planning, shopping, cooking, and cleaning—give them a list of your favorite foods. Your doctor and registered dietitian are your nutrition experts and can help before, during, and after treatment.
For caregivers: don't be surprised if your loved one's food preferences change day to day. Offer gentle support rather than pushing them to eat, and talk through eating problems together.
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Weight Changes, Appetite Loss, and Cancer: the quick overview
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Suggested animation storyboard▾
- 1Open on a calm title card: "Weight Changes, Appetite Loss, and Cancer" with the Cancer Explained mark.
- 2Narrator reads the 30-second summary while a soft animated diagram builds on screen: "Cancer and its treatment can change your appetite and weight—some people lose weight, others gain it, and some develop malnutrition. Appetite loss often leads to eating less than your body needs. Small frequent meals, high-protein and high-calorie foods, and working with a registered dietitian can help you stay strong."
- 3Scene 2: illustrate the idea — "Appetite loss and weight loss are common side effects of cancer and its treatments."
- 4Scene 3: illustrate the idea — "Some people gain weight during treatment, often with ovarian, breast, or prostate cancer, or from steroids and hormone therapy."
- 5Scene 4: illustrate the idea — "Eating small meals every 2 to 3 hours and choosing high-protein, high-calorie foods can help with appetite loss."
- 6Close on a reminder card: this is educational only; talk with your healthcare team, and a link to the NCI source.
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Quick knowledge check
According to this article, what does appetite loss often lead to?
Frequently asked questions
▸Why do I have no appetite during cancer treatment?
Appetite loss is a common side effect of cancer and its treatments. Side effects like nausea, vomiting, mouth sores, painful swallowing, dry mouth, taste changes, and feeling full quickly can all reduce appetite, as can anxiety, pain, depression, and fatigue.
▸What should I eat when I don't feel like eating?
Eat foods high in protein and calories, eat small meals every 2 to 3 hours (about 5 or 6 a day), and eat high-protein foods first when your appetite is strongest. Milkshakes, smoothies, soups, and nutrition supplement drinks like Ensure or Boost can help when you don't feel like eating solid food.
▸Can I gain weight during cancer treatment?
Yes. Although many people lose weight, some gain it—more commonly with ovarian, breast, or prostate cancer. Causes include fluid retention, increased appetite, metabolic changes from hormone therapy, steroids, and being less active because of fatigue or pain.
▸What is malnutrition and why does it matter?
Malnutrition is when your body doesn't get enough energy, protein, vitamins, and minerals. It can make you weak and tired, make it harder to fight infection or finish treatment, lower your quality of life, and even become life-threatening. Decreased appetite is a main cause in people with cancer.
▸When should I tell my doctor about weight changes?
Speak with your doctor right away if you start to lose weight, and report weight loss of more than 3 to 5 pounds in one week. Also tell your doctor about sudden weight gain, such as 5 pounds in a week, or weight gain that doesn't stop.
▸What if I can't eat enough no matter what I try?
If you continue to have trouble eating and are losing weight, your doctor or dietitian might suggest tube feeding (enteral nutrition) or IV nutrition (parenteral nutrition) to help you get the nutrients you need.
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Questions to ask your healthcare team
Consider bringing these questions to your next appointment.
- Am I at higher risk for appetite loss or weight loss based on my type of cancer?
- Can I meet with a registered dietitian, and how do I get a referral?
- Would a nutrition screening before treatment be helpful for me?
- Are there medicines (appetite stimulants) that could help me eat more?
- How much weight change should I report to you, and how quickly?
- Are tube feeding or IV nutrition options I should know about if eating gets very hard?
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