Is weight loss a common side effect of skin cancer treatment?

Weight loss can happen during skin cancer treatment, but it isn’t universal and often relates to treatment side effects like appetite loss, fatigue, nausea, diarrhea, or hormone changes. ^[1] These effects are typically temporary, though they can impact eating and nutrition during radiation or immunotherapy. ^[1] Appetite loss is specifically noted with external-beam radiation therapy and can lead to unintended weight reduction if not managed. ^[1]

Immunotherapy (checkpoint inhibitors such as nivolumab or ipilimumab) used in melanoma and some advanced non-melanoma skin cancers can cause systemic side effects that affect weight, including decreased appetite, diarrhea, and endocrine (hormone) problems of the thyroid, pituitary, or adrenal glands that can lead to weight gain or weight loss. ^[2] Patient information for common melanoma immunotherapy regimens highlights anorexia (loss of appetite) and advises high-calorie, high-protein intake and dietitian support if weight is falling. ^[3] Similar guidance appears across nivolumab treatment summaries. ^{[4] [5]}

Importantly, rapid, unexplained weight loss can be a sign that needs prompt medical evaluation, whether related to the cancer itself or its treatment. ^[6] If weight is dropping without trying, clinicians generally recommend assessing causes and addressing nutritional risks early. ^[7]

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Why weight loss happens during treatment

• Loss of appetite and taste changes: Common with radiation; eating becomes less appealing, reducing calorie intake. ^[1]
• Gastrointestinal side effects: Nausea, vomiting, diarrhea can reduce absorption and intake, more often seen with systemic therapies like immunotherapy. ^[8]
• Endocrine effects: Immunotherapy can inflame hormone glands (thyroid, pituitary, adrenal), causing metabolism shifts that result in weight gain or weight loss; symptoms include extreme fatigue, dizziness, and persistent headaches. ^[2]
• Fatigue: Feeling very tired reduces shopping, cooking, and eating frequency, contributing to lower intake. ^[1]
• Cancer-associated cachexia: In advanced cancers, a complex syndrome of inflammation and metabolism changes can drive weight and muscle loss; management focuses on nutrition, symptom control, and maintaining function. [PM14]

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When to be concerned

You may need medical review if you notice:

• Weight falling without trying over weeks to months. ^[6]
• Ongoing diarrhea, severe nausea/vomiting, mouth sores, or difficulty swallowing that prevent eating. ^[8]
• Signs of hormone problems: extreme tiredness, feeling cold, hair loss, dizziness/fainting, mood changes, or unexplained weight changes. ^[2]

Early reporting allows your team to treat side effects, adjust medications, and involve nutrition services.

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How to manage weight loss during treatment

Core goals are to maintain weight, protein intake, fluids, and energy for recovery and daily activities. ^[9] Eating plans during treatment prioritize high-calorie, high-protein foods, practical meal schedules, and symptom-targeted strategies. ^[10]

Practical nutrition strategies

• Eat small, frequent meals: Try a snack or small plate every 2–3 hours rather than three large meals to overcome low appetite. ^[11]
• Schedule eating: Use alarms or reminders so you eat by the clock, not only when hungry. ^[11]
• Prioritize protein and calories: Choose eggs, Greek yogurt, nut butters, beans, tofu, poultry, fish, and add calories with olive oil, avocado, full-fat dairy, and smoothies/shakes. High-calorie, high-protein choices help maintain weight and repair tissues. ^[9]
• Separate fluids from meals: If early fullness is an issue, drink most fluids between meals so meals supply more calories. ^[3]
• Fortify foods: Enrich soups, oatmeal, and mashed foods with powdered milk, cheese, oils, or nut butters; consider oral nutrition supplements if intake is low. These simple add-ins raise calories without large portion sizes. ^[10]
• Gentle activity: Light exercise can stimulate appetite and aid digestion as tolerated. ^[10]

Symptom-specific tips

• For nausea or vomiting: Opt for bland foods, cold items, ginger tea; ask for anti-nausea medications and dose adjustments. Medication support can make eating easier. ^[12]
• For diarrhea: Choose low-fiber, easy-to-digest foods (bananas, rice, applesauce, toast), hydrate with electrolyte solutions, and report persistent symptoms to check for immune-related enteritis. ^[8] Emerging approaches like targeted budesonide formulations may be considered for immunotherapy-related enteritis. [PM17]
• For mouth sores or taste changes: Use soft, moist foods, sauces, and mouthwashes provided by the care team; avoid spicy or acidic foods that irritate. Skin rashes and mouth sores can be managed with topical aids so eating is more comfortable. ^[12]

Professional support

• Ask for a dietitian referral: Nutrition experts tailor plans to your symptoms, preferences, and treatment stage, helping you keep up calories, protein, vitamins, and fluids. Dietitian guidance is recommended whenever weight is dropping or appetite is low. ^[9]
• Coordinate with oncology team: They can adjust drug doses or schedules, prescribe anti-nausea and anti-diarrheal medications, and monitor for endocrine side effects. Timely intervention often prevents further weight loss. ^{[12] [2]}

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Simple meal plan ideas

• Breakfast: Greek yogurt parfait with granola and honey; peanut butter toast; smoothie with milk, protein powder, banana, and nut butter. Smoothies are convenient if chewing is difficult. ^[10]
• Lunch: Egg salad or chicken salad sandwich with avocado; lentil soup enriched with olive oil; cottage cheese with fruit.
• Snacks: Trail mix, cheese and crackers, hummus and pita, full-fat pudding.
• Dinner: Baked salmon with olive oil; tofu stir-fry with rice; pasta with creamy sauce and added parmesan.
• Fluids: Milk, kefir, oral nutrition shakes, and electrolyte drinks between meals. Hydration supports digestion and energy. ^[10]

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Table: Common treatment side effects that affect weight and what to do

Treatment/Effect	How it can cause weight loss	What you can do
Radiation therapy	Appetite loss and fatigue reduce intake	Small frequent meals; calorie/protein fortification; report symptoms early; dietitian referral
Immunotherapy (checkpoint inhibitors)	GI side effects (nausea/diarrhea), endocrine changes (thyroid/adrenal)	Anti-nausea meds, manage diarrhea, screen/treat hormone issues, high-calorie/high-protein diet
General treatment fatigue	Less ability to shop/cook/eat	Ready-to-eat high-calorie snacks, family help, meal delivery, schedule eating
Cancer-related cachexia	Metabolic changes and inflammation reduce weight/muscle	Early nutrition support, symptom control, maintain activity and function

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Bottom line

Weight loss can occur during skin cancer treatment, most often because of appetite loss, GI symptoms, fatigue, or hormone changes, and it is usually manageable with early, practical nutrition strategies and symptom control. ^[1] If your weight is falling without trying, let your care team know promptly so they can treat side effects, check for endocrine issues, and connect you with a dietitian. ^{[6] [2]} Aim to maintain weight with high-calorie, high-protein foods, scheduled small meals, and targeted management of nausea or diarrhea. ^{[9] [11]}