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Types of diet problems

Find out about the the side effects of cancer and its treatments that make it difficult to eat enough and stay at a healthy weight.

Eating problems with cancer

Not everyone with cancer has diet problems. Problems with eating or drinking are often temporary and disappear once treatment has finished.

But if you have advanced cancer some of these problems can be difficult to get rid of or control. How severe they become will depend on:

  • the type of cancer you have
  • the type of treatment you are having
  • your age and general health

Your type of cancer can affect how likely it is that you will have digestive problems.

Symptoms of the cancer or the side effects of treatment can sometimes make it difficult to eat. These include:

  • sickness
  • bowel problems
  • a lot of pain
  • difficulty breathing
  • fatigue (tiredness)

Loss of appetite

Doctors call loss of appetite 'anorexia'. This is very different to the psychiatric condition 'anorexia nervosa'.

Anorexia is common in people with cancer. It can happen in the early stages of the disease or much later if the cancer grows and spreads to other parts of your body.

As many as 1 in 4 people diagnosed with cancer have loss of appetite. For people with advanced cancer, up to 9 out of 10 people (90%) lose their appetite to some extent.

There may be a particular cause for your loss of appetite. Or it may just be that you are feeling too tired or fed up to bother eating much.

Weight loss

This is weight loss when you are not trying to. It is a very common symptom in people with cancer. It may be one of the reasons you first go to the doctor.

Weight loss and cancer

There are many causes of weight loss, many of which can be treated.

Losing weight is often associated with loss of appetite. But this is not the only cause. You may be eating normally but still losing weight. Your body may not be absorbing all the fat, protein and carbohydrate from the food you eat. Or your body may be burning up calories faster than normal.

Continuous weight loss can be worrying and a constant reminder of your illness, affecting how you feel about yourself.

Weight loss can depend on your cancer type

How much weight you lose can depend on the type of cancer you have.

About 6 out of 10 people (60%) with lung cancer and 8 out of 10 people (80%) with stomach cancer, pancreatic cancer or oesophageal cancer have lost a significant amount of weight by the time they are diagnosed.

People with breast cancer or prostate cancer, for example, don't tend to have lost weight at diagnosis.

When to worry about your weight

If you are not dieting and you lose more than 5% of your normal weight in 1 month, or 10% in 6 months, your doctor will want to find out the cause.

For example, if you normally weigh 10 stone (63.5 kg) and lose half a stone (3kg) in a month, or a stone (6kg) in 6 months that would need investigating.

This may not seem like a lot of weight but if you continue to lose weight at this rate it could become a serious problem.

Cachexia (wasting syndrome)

You may also hear this called ‘wasting syndrome’ or ‘anorexia cachexia syndrome’.

Cachexia (kak-ex-ee-a) comes from the Greek word kakos meaning 'bad' and hexis meaning 'condition'. Anorexia just means loss of appetite and is often associated with cachexia, but not always.

Cachexia is more than simply loss of appetite though. It is a very complex problem and involves changes in the way your body normally uses protein, carbohydrate, and fat. It leads to many problems including muscle wasting.

Cachexia is very different to general weight loss. It can’t be completely reversed even if you feel like eating.

Trying to eat more or being fed through a tube may not help reverse it either. People suffering from cachexia do not seem to feel hungry.

Who gets cachexia

It isn’t usual to get cachexia with the early stages of cancer. Up to 6 out of 10 people (60%) with advanced cancer develop some degree of cachexia.

Cachexia in advanced cancer can be very upsetting and make you feel very weak. It isn't just associated with cancer though.

It is common in the advanced stages of other illnesses such as heart disease, HIV and kidney disease.

Losing muscle and fat can make it look as though you are ‘wasting away’. This can all be made worse because of the side effects of cancer treatment you are having.

Symptoms of cachexia

Cachexia seems to be more common in people with lung cancer or with cancers anywhere in the digestive system. The main symptoms are:

  • severe loss of weight, including loss of fat and muscle mass
  • loss of appetite
  • feeling sick (nausea)
  • feeling full after eating small amounts
  • anaemia (low red blood cells)
  • weakness and fatigue

What happens with cachexia

We don't know exactly what happens in cachexia, but scientists now think that the cancer releases chemicals into the blood that contribute to the loss of fat and muscle.

These chemicals may make your metabolism speed up so that you use up calories faster. Because your body is using up energy faster than it is getting it, you can have severe weight loss even if you are eating normally.

Mouth and throat problems

Cancer treatments such as chemotherapy or radiotherapy can make your mouth very sore, which can make it very difficult to eat.

For general information and support contact the Cancer Research UK nurses on freephone 0808 800 4040 Monday to Friday, 9am to 5pm.
Last reviewed: 
24 Feb 2014
  • Nutrition and Cancer
    Edited by Clare Shaw
    Wiley-Blackwell, 2011

  • National Institute for Health and Care Excellence (NICE) guidance
    Quality standard for nutrition support in adults (QS24) – November 2012

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