Cancer and appetite loss

Loss of appetite is common in cancer and should not be ignored. It can lead to unintentional weight loss, which in turn weakens the body just when it needs to be at its strongest. Read on to learn why appetite loss matters and what can be done to overcome it. 

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Is loss of appetite normal in cancer?

Appetite loss is very common in people with cancer. Depending on the type of cancer, between 40% and 80% of patients say they are eating and drinking less than before their diagnosis1-6. Patients may find that their favorite foods no longer appeal, or that appetite is reduced or almost nonexistent. These changes can be distressing for patients, as well as for family and friends.

When and why does cancer cause appetite loss?

There are lots of reasons why people with cancer lose their appetite. Before cancer has been diagnosed, unexplained loss of appetite can be an early sign that something is wrong7. This is because the tumor itself can cause the body to produce chemicals that suppress appetite7,8. After diagnosis, the side effects of treatment – such as taste changes, mouth ulcers, nausea and vomiting – can reduce appetite3. A cancer diagnosis may also be accompanied by pain, fatigue, anxiety, and depression, all of which can reduce your motivation and desire to eat3.

Why does loss of appetite in cancer matter?

Appetite loss matters, because it stops your body from getting all the energy, protein and other nutrients it needs – just when you need to be at your strongest to fight cancer. It can also cause you to lose weight without meaning to (known as unintentional weight loss). Even if you are eating a normal amount of food, your body might not be using the nutrients in your food properly or it may be burning energy faster than usual, increasing your nutritional needs.

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I am overweight – isn’t it good for me to lose weight?

When you’re healthy, reducing food intake to lose weight is something you may wish to consider. However, it is not advisable to try to lose weight while you are being treated or recovering from cancer9. Because the body stores excess calories mainly as fat, weight loss generally means losing fat. 

But losing weight can mean losing muscle too, and this is particularly the case in people with cancer8. Losing muscle makes you physically weaker, which can affect many aspects of your daily life – for example getting out of bed, going for a walk, or standing to cook a meal, and your ability to tolerate anti-cancer treatments such as chemotherapy8,10.

What is muscle loss and cancer cachexia?

Muscle is made from protein. If you don’t – or can’t – eat enough protein, the body breaks down muscle to get the building blocks of protein (amino acids) to use for other purposes such as healing and fighting infection. This loss of muscle tissue is a key feature of “cachexia”, a form of cancer-related malnutrition8. Cachexia can make you feel weak and tired and reduce the success of treatment. It can even affect your chances of survival8,10.

Can weight loss affect my treatment?

Yes. Unintentional weight loss or weighing less than is healthy for your height (known as a low body mass index or “BMI”) makes your treatment less effective and more likely to cause side effects10. This is because the ideal dose of chemotherapy or radiotherapy is determined by your weight and height. If you lose weight after starting treatment, you may be unable to tolerate the full dose. As a consequence treatment may need to be reduced or stopped altogether10,12. People with a low BMI also tend to experience more complications and lower survival after surgery for cancer13. As well as making your treatment less effective, weight loss in cancer can lead to physical and mental tiredness, be stressful, and reduce your overall quality of life11.

What can I do if I lose my appetite?

While you are being treated for cancer it is important that you try to maintain your weight as much as possible. This gives your body the best chance of staying strong and responding well to treatment. Without forcing yourself to eat it can help a lot to eat small amounts regularly to avoid weight loss. And make every mouthful count by choosing foods that are “nutrient dense”, meaning they contain high levels of energy, protein and other key nutrients.

Tips for maintaining your weight

  • Eat when you feel hungry – if you are typically most hungry in the mornings or afternoons, plan to eat your biggest meal then
  • Eating several small meals or snacks throughout the day may be easier to manage
  • Limit drinks before and during meals as they can fill you up
  • If you can’t face a meal, consider having a nutrient-dense drink instead
  • Weigh yourself regularly and if you notice you are losing weight, talk to your doctor without delay
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When should I see a doctor?

If you are struggling to eat and drink, notice unexplained weight loss, notice changes in taste or have concerns about your diet and nutrition, talk to your healthcare professional. Depending on the cause of your symptoms, your healthcare team may be able to help you with medication, dietary changes, and/or nutritional support. As many cancer treatments are long and complex, you may benefit from being referred to a dietitian who can work out an individualized nutrition plan. 

If medical nutrition is appropriate as part of any treatment you may be receiving, it is a decision that must always be made in consultation with a healthcare professional. It’s particularly important to always discuss if your appetite is reduced and/or if you are losing weight, as whatever age you may be, unintentional weight loss is never a normal part of life.

Helping patients stay strong for the road ahead

For information on how to make sure your body is getting enough of the right nutrition, and to talk to a healthcare professional about your nutritional concerns, visit our dedicated information hub for patients.

Find out more
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Cancer and taste changes

Changes in taste and smell are more than just an unpleasant side effect of cancer treatment. They can stop you eating a healthy balanced diet, potentially leading to weight loss and even malnutrition – at a time when your body needs to be at its strongest.

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Cancer and weight loss

Side effects of cancer and its treatment can take a toll on the body, negatively affecting appetite, the way we taste food and even the way our body absorbs nutrients. For many cancer patients (30-80%[14]) this leads to weight loss. The majority of the weight lost by cancer patients is muscle[8] – or ‘lean body mass’ – the protective tissue needed to keep the body strong and withstand treatment. Losing a significant amount of weight can even delay treatment[15-17].