Loss of appetite and cancer: common causes and what to do

Appetite loss is very common in people with cancer, resulting in 40-80% of patients eating and/or drinking less than they did pre-diagnosis.^1-6 Loss of appetite can be a direct or indirect symptom of cancer, or a side effect of cancer treatment – with certain cancers and treatments more likely to impact your appetite and ability to enjoy food than others.^5,6

While it may not seem like something you need to be overly concerned about, loss of appetite can result in unintentional weight loss, decreased muscle mass, nutritional deficiencies and fatigue or weakness.^1-5 You need your body to be at its strongest when you’re fighting cancer or navigating treatment – which requires you to consistently meet your energy and nutrient needs.^1-6 While appetite loss can undoubtedly make this more challenging,³ understanding the causes behind this common cancer symptom and how to effectively manage it can help prevent any flow-on health complications or concerns.

Why does cancer cause a loss of appetite?

People with cancer can experience loss of appetite for various reasons. It can be a direct physical symptom of cancer, indirectly caused by the illness (like a psychological or emotional side effect), or a side effect of certain treatments.^3-5

Signs you may be experiencing appetite loss include:

• Eating less than you normally would (or being unable to eat at all)
• Showing little or no interest in eating foods
• Unintentionally losing weight
• Rejecting your favourite foods.^7-9

Some people lose their appetite briefly, while for others it can persist for days, weeks, or longer.⁸ Let your healthcare team know right away if you notice changes to your appetite. They can put strategies in place to help minimise any health complications that may arise with low appetite, including nutritient deficiencies, and muscle or weight loss.

The role of tumors

Some tumors and types of cancer can cause appetite loss.

• Tumors can block your body’s normal hunger signals in multiple ways, sometimes causing appetite loss. They can release hormones or chemicals which trick your body into feeling full – even when you’re not.^6,10,11
• Tumors may also physically block food from travelling through your digestive system, particularly when located in the stomach, pancreas or liver.^6,10,11
• Some symptoms caused by tumors can interfere with normal appetite including nausea, pain, stress, depression and dehydration.¹⁰
• Tumors found in or around the digestive tract, including head and neck cancers, can also make it difficult or painful to eat and swallow.⁶

Cancer symptoms

Some cancer symptoms can reduce your appetite or make eating uncomfortable:

• Cancer-related pain may interfere with your appetite or ability to eat normally⁷
• Nausea or vomiting can make it difficult to stomach food or keep it down⁷
• Constipation or diarrhoea can make you feel unwell and reduce your hunger⁷
• Stress or depression can strongly suppress your appetite⁷
• Dehydration may reduce appetite⁷
• Changes in taste and/or smell can make foods you’d normally enjoy suddenly feel intolerable⁷
• Other health problems caused by cancer (and the medicines required to treat them) may also cause appetite loss.⁷

Chemical changes in the body

Cancer and treatment can cause internal chemical changes that may interfere with your regular appetite.

For example, cancer produces inflammatory chemicals that can disrupt normal metabolism and decrease appetite. This is particularly common in cancers like lung and advanced-stage cancers.¹²

Other neurotransmitters, hormones and inflammatory responses caused by cancer can also interrupt the normal pathways which are responsible for making you feel hungry.¹² This may also result in changes to your appetite and ability to eat normally.

Side effects of cancer treatments

Various cancer treatments and their side effects may also cause appetite loss.

• The drugs used in treatments like chemotherapy, radiation and immunotherapy can directly suppress appetite.⁷
• You may experience low appetite or disinterest in eating while recovering from cancer surgery. If the surgery involves your digestive organs, any complications like pain or inflammation can make swallowing or digestion painful or difficult.⁷

Similarly, the side effects of treatment can also make eating difficult, including:

• Taste and smell changes, which can result in a wide range of foods suddenly unappealing or unpleasant^3,13
• Vomiting and nausea may make it difficult to keep food in your stomach¹⁴
• Constipation or diarrhoea can make eating uncomfortable¹⁵
• Low energy and fatigue can leave you feeling too exhausted to eat¹⁵
• Mouth ulcers, sores and sensitivity, a dry mouth or a sore throat can make eating painful¹⁵
• Having a persistent bad taste in your mouth may make foods and drinks taste metallic or unappealing and impact your appetite.^3,7

While many treatments leave you with minimal appetite or desire to eat, this is a time when your body needs more nutrition than normal – so it’s important to find ways to ensure you’re getting the energy and nutrients required to support your recovery.^3,7

Psychological factors

Cancer doesn’t just cause physical side effects – it has significant psychological and emotional impacts too. Stress, anxiety and depression are common amongst cancer patients, often worsened by fears or uncertainty about the future, difficulty navigating treatment and cancer symptoms, or grief.¹³ These experiences can strongly suppress your appetite and willingness to eat.

Patients with advanced cancer are most vulnerable to appetite loss. This can be the result of cancer symptoms and side effects, but is often caused by these feelings of depression, helplessness or hopelessness.¹⁶

Many patients  may also become overly concerned about avoiding various foods or food groups like added sugars, worrying that these foods could negatively impact their health or recovery.¹⁷ However, there is minimal evidence supporting the need to eliminate these foods for cancer patients.¹⁸ In fact, restricting your diet may cause stress and overwhelm which can interfere with your appetite and make it more challenging to meet your nutrient and energy needs. ¹⁷

What types of cancer cause loss of appetite?

Appetite loss can happen at any stage in the cancer journey and is more strongly linked to some types of cancer than others.¹⁹ Early in your diagnosis, your normal hunger signals can be affected by the cancer itself and any chemicals or hormones it produces.¹⁹ In the later stages, any cancer symptoms, treatment side effects, and emotional consequences of the disease can significantly disrupt your appetite.¹⁹

Gastrointestinal cancers

Gastrointestinal cancers, including stomach, pancreatic and liver cancers, commonly cause appetite loss.⁷

• Stomach cancer: Tumors in the stomach can give your body the illusion of feeling full, even when your stomach is completely empty.⁷
• Pancreatic cancer: The pancreas is involved in digestion. When cancer impairs its regular function, you can no longer process food normally.⁷ This can cause appetite loss.
• Liver cancer: When cancer interferes with liver health and function, your metabolism and appetite are affected.⁷
• Tumors: As mentioned above, tumors can secrete certain hormones or inflammatory chemicals which interrupt your brain’s hunger signals and trick your body into feeling full, even when it’s not.⁷ Tumours can also physically block digestion or create feelings of fullness by taking up space in key digestive areas of your body – particularly around the gastrointestinal tract.⁷

Lung Cancer

Lung cancer patients often experience a loss of appetite, caused by the release of inflammatory chemicals that suppress normal hunger.⁷ Lung cancer also makes patients’ bodies burn energy faster, which can result in unintentional weight loss and contribute to poorer treatment results and health problems if unmanaged.⁷

Head and Neck Cancers

Cancers of the head and neck may directly affect your ability to swallow and chew, and often impact your sense of taste.⁷ This can make eating difficult or painful, reducing appetite and leaving many patients unwilling to eat.

Treatments like chemotherapy, surgery and radiation therapy, which are generally used to target head and neck cancers (and gastrointestinal cancers), tend to cause side effects that can make eating challenging or suppress appetite.²⁰ These include dry mouth or mouth sores, nausea or vomiting and taste changes.²⁰

Ovarian Cancer

Ovarian cancer commonly causes loss of appetite too.⁷ Ovarian cancer tumors can press against the stomach and interfere with appetite. They can cause swelling in the stomach, making patients feel full after eating little or no food at all.⁷ Bowel changes and nausea, which are common with ovarian cancer, can again contribute to appetite loss.^7,15

Advanced-Stage Cancers (Metastatic Cancer)

Advanced-stage cancers commonly affect multiple areas of the body, with up to 80% of advanced cancer patients experiencing some level of cachexia.²¹ Cachexia is a muscle wasting syndrome, where the patient becomes unable to consume enough energy or nutrients to meet their requirements.²¹ It results in rapid muscle- and fat loss and can leave you feeling weak, fatigued, and unable to continue regular daily activities.^16,21

Appetite loss in late-stage cancer is often severe and progressive.¹⁶

Why does weight loss in cancer matter?

Appetite loss can result in unintentional weight loss, losing muscle, and nutritional deficiencies or gaps if unaddressed.¹⁶ This can cause many health complications for cancer patients, including low energy or fatigue, and inability to continue treatment or achieve optimal recovery results.^4,5,16

While good nutrition is essential throughout your lifetime to support general health, strength, regular body processes, energy levels and your quality of life, it’s even more crucial to ensure you’re getting the energy and nutrients you need during cancer and treatment.

Appetite loss can make it difficult to meet your energy, protein and nutrition requirements – at a time when you need to be your strongest, so you can fight cancer and receive treatment as effectively as possible.²²

Even if you can eat normally, your energy, protein and nutrient needs often increase with cancer.²³ Your body may also become less efficient at absorbing the nutrients in your food or burn energy faster as it fights your illness.²³ Each of these factors can contribute to increased food and nutrient requirements.

If decreased appetite is leaving you falling short of your nutrient needs, you may experience unintentional weight- or muscle loss.^10,11,24 This can make you physically weaker and more vulnerable to illness, infection and treatment side effects, and also make your daily activities more challenging, including cooking, going for a walk or getting out of bed.^10,11,24

Losing too much weight can reduce the effectiveness of your treatment and worsen your side effects. People who unintentionally do so during their cancer battle may end up unable to complete their planned course of treatment,^24,25 and tend to experience more complications, poorer results and lower survival rates from cancer treatment.²⁶

As well as interfering with your treatment and recovery, weight loss during cancer can leave you feeling physically and mentally fatigued, less able to cope with the symptoms of your condition and side effects of treatment, and even reduce your quality of life.²⁷

While weight loss during cancer is worrying, its association with muscle loss is one of the main reasons it can be harmful.¹¹ When cancer patients lose weight, they mostly lose protective muscle tissue (or lean body mass) which you need to help your body fight cancer and withstand treatment.¹¹

If you notice changes to your appetite, don’t ignore it. Consult your healthcare team right away for support with managing appetite loss and maintaining adequate nutrition.

Developing cancer cachexia

Cancer cachexia is most common in people with advanced-stage cancers and is more complex than a loss of appetite.¹⁶ With this muscle wastage syndrome, the body becomes unable to properly use protein, carbohydrates and fats from your diet, creating nutritional “gaps” between what your body needs, and what you’re consuming and absorbing.¹⁶

Muscle is made of protein, so when you can’t eat enough protein to accommodate your significantly increased needs, your body begins breaking down muscle tissue to use to fill the gaps. Protein is essential for healing and preventing infection, so your body will do whatever it can to get as much as it needs.¹⁶

However, when your muscle mass begins to break down, you can feel weak, fatigued, and become less able to tolerate cancer treatment, also compromising the results and recovery you can achieve.^11,24

Cachexia differs from general unintentional weight loss, as eating more is not the solution.²¹ Even tube feeding doesn’t often resolve cachexia.²¹ The complex condition is still not fully understood by scientists, but there is some indication that the body can’t properly use glucose from the blood as a source of energy.^19,21 Then, the cancer itself releases inflammatory chemicals into the blood, contributing to fat- and muscle loss.²¹ These chemicals can speed up your metabolism so you’re using energy faster than you can obtain it from your diet, resulting in severe and rapid weight loss.²¹

Cachexia is more common with lung cancer and other digestive system cancers.⁷ Symptoms include severe weight loss (fat and muscle loss), appetite loss, anaemia, weakness and fatigue.^19,21 While early-stage cancer patients don’t often experience cachexia, up to 80% of advanced-stage patients develop the condition to some extent.²¹

While some people struggling with cachexia are given appetite-stimulating medications, these aren’t always effective.²¹

Cachexia can be life threatening for people with cancer, causing deficiencies in protein and essential nutrients, resulting in bodyweight and muscle loss.²¹

Stimulating appetite and maintaining weight with cancer

If you’re struggling with appetite loss or finding it difficult to maintain your weight and muscle, these practical strategies may help stimulate your appetite so you can consistently meet your nutrient needs.

Firstly, treat any symptoms that make it difficult to eat.⁸ If you’re having difficulty swallowing or chewing due to mouth sores, dryness or sensitivity, address these symptoms first. By implementing changes, such as avoiding spicy or acidic foods to prevent aggravating mouth sores or chewing sugar-free gum to stimulate saliva production,¹⁵ you can relieve some of the barriers to eating. This may help restore your appetite and willingness to eat.

Learn more about managing side effects of cancer treatment including chemotherapy here.

Smart eating strategies

• Try eating small meals every 2-3 hours, rather than sticking to three large meals per day to ensure you’re eating enough.¹⁶ This can help to manage nausea, support digestion, and makes eating more manageable when you’re struggling with reduced appetite.¹⁶
• Choose high-protein, high-energy foods to help maintain your weight and provide your body with more calories.¹⁶ Add olive oil, nuts and seeds, avocado, full-fat dairy products and other healthy fats to your meals to easily increase the energy content. And include a source of protein in each meal and snack, like poultry, seafood, legumes, tofu and yoghurt, to help prevent muscle wastage.
• If your healthcare professional recommends it, using an oral nutritional supplement (ONS)¹⁶ like Fortisip® can help you meet your daily nutritional needs when your usual diet is not enough.²⁸ It provides a good source of protein to support the maintenance of muscle mass,²⁹ and is high in calories to help maintain your body weight when you’re unwell or recovering from illness.²⁸ Fortisip’s® Compact Protein range provides a more concentrated formula in a small serving size, making it easier to consume additional calories, protein and nutrients when you don’t feel like eating.
• Learn your hunger patterns, and eat when you feel hungry.²² If you’re normally most hungry in the morning, eat your biggest meal then. Don’t wait for set mealtimes⁸ – if you’re hungry at a time that doesn’t fall into your regular eating times, make the most of it!
• Enjoy your favourite foods at any time of day. If you love breakfast foods, eat them at lunch, dinner, or any time between.⁸ Opt for foods you enjoy, as this can help stimulate your appetite when you’re not hungry.¹⁶
• Keep a ready supply of high-protein, high-energy snacks on hand, or stock the ingredients for easy-to-make options you can reach for when you need.⁸ Yoghurt with fruit and granola, cereal and milk, sandwiches, cheese and biscuits, hearty soups and smoothies are good options.
• Limit how much you drink before or during meals, as liquids can make you feel full faster. Enjoy most of your drinks between your meals.²²
• Try high-energy drinks like smoothies when you can’t stomach food.²²

Light exercise to boost appetite

Gentle exercise can stimulate your hunger hormones and appetite. If you’re feeling up to it, introduce light movement like stretching, yoga or a walk around the block, and gradually increase your activity over time under the guidance of your healthcare professional.¹⁶ Exercise is also fantastic for digestion and stabilising your energy levels.¹⁶

Medical treatments and management strategies

Your healthcare team may recommend medications like appetite stimulants,¹⁶ especially if you’re struggling with cachexia. However, these don’t work for everyone.²¹ Your team may also suggest medicines to address other symptoms that are making it difficult for you to eat, like nausea or pain, which may improve your appetite.¹⁶

Your dietitian or healthcare professional may also suggest using oral nutritional supplements (ONS) to help ensure you don’t lose too much weight, alongside a high-protein, high-calorie diet containing plenty of nutrient-rich foods. Fortisip® is a ready-to-drink ONS that can help you meet your daily nutritional needs when your usual diet is not enough.²⁸.

Emotional and psychological support

Stress, anxiety and depression can be big appetite suppressants for cancer patients, so seeking emotional and professional support to address these can help. Seek out support groups where you can connect with others navigating similar experiences, to help you feel less alone and isolated.¹⁶ And reach out to a psychologist for individual help if you’re able.

If this isn’t an option for you, ask your friends and family for additional support. Share how you’re feeling and let them know how they can show up for you. Involve your family members in meal planning and prepping, as this can also encourage you to stick to proper and adequate nutrition – even when you don’t feel like eating.¹⁶

Don’t be afraid to ask for help at any stage along your cancer journey – it’s always available to you.

When to see a doctor about appetite loss

If you notice you’ve unintentionally lost weight, seek medical support right away. If in doubt, don’t hesitate. Noticing the early signs and intervening quickly can help prevent you from losing more severe amounts of weight and muscle, and will improve your quality of life in the long run. Now you know how crucial it is to maintain your bodyweight and muscle mass during cancer, so speak up if you’re worried.

It’s particularly important to seek medical attention if:

• You experience rapid or unexplained weight loss⁸
• You develop cachexia symptoms, including muscle wastage or feelings of extreme weakness⁸
• Your appetite doesn’t improve, even with medical interventions or strategies^8,27
• Your treatment side effects or cancer symptoms are making eating impossible
• You need a personal care plan to support you.⁸

Unintentional weight loss is not normal during cancer.⁸ If you’re concerned about your appetite, ability to meet your nutritional needs, or changes in your bodyweight and muscle mass, speak to your healthcare professional right away.^8,27

Fortisip® is a food for special medical purposes and must be used under medical supervision.

This is provided for informational purposes only. It does not replace the advice of a healthcare professional. Please consult your healthcare professional for tailored advice.

References

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