Changes to your appetite and weight

Many people with cancer find there are times when they cannot eat as much as usual. Sometimes this leads to weight loss. This can be caused by cancer or the side effects of cancer treatments.

Some people do not feel hungry at all. Others may feel full soon after starting a meal. Others find that food makes them feel sick (nauseous) or that treatment makes some foods taste different.

Some types of cancer make your body use up more energy, even if you are not very active. The cancer may produce chemicals that make your body work more quickly than normal. It may also produce chemicals that make your body break down fat and protein more quickly. This can make you lose weight, even though you may still be eating well.

If you lose too much weight, it is important to talk to a dietitian. If you do not have a dietitian, you can ask your cancer doctor, nurse or GP to refer you to one. Qualified dietitians are experts in assessing the nutritional needs of people who are ill. They can suggest changes to your diet. They may suggest you take nutritional supplements to help prevent further weight loss and help you gain weight. They may recommend foods that you may normally think of as unhealthy.

Booklets and resources

Food types on the building-up diet

It can be helpful to know about the different types of food groups and what energy the body gets from them. Try to get a balance of different types of food to make sure you are getting the nutrients your body needs. If you are losing weight, eating higher energy foods can help to prevent losing more. It can also help you to put weigh back on. We have more information about the different food types.

Adding energy and protein to everyday foods

People who find it difficult to eat enough need to find ways to get more energy and protein in their diet. The building-up diet is high in energy and protein. It is for people who have lost or are losing weight, or who can only manage to eat small amounts. Not everyone will be able to put on weight with this diet. But it should help to slow down or stop further weight loss.

If you have a good appetite, you should not have trouble eating the extra calories and protein you may need if you are ill. But if you do not have a good appetite, there are ways to add extra energy and protein without having to eat more food. We have more information on how to add energy and protein to your food.

Meal ideas and shopping list

We have put together a list of high energy meal ideas and ways that you can adapt your usual meals. This can help you to add more protein and energy without having to eat more food. We have also added a shopping list of high energy foods it may be helpful to stock up on.

Nutritional supplements (food supplements)

The best way to get more energy and protein is by eating a healthy, balanced diet. If you are still having eating problems or are losing weight, talk to your cancer doctor, specialist nurse, dietitian or GP. They can give you more advice. They may recommend some nutritional supplements.

There are many kinds of nutritional supplements available that can add extra energy or protein (or both) to your diet. These include nutritional drinks, soups, powders and puddings. You can add them to your everyday foods, or have them in addition to your normal diet. Sometimes they can be used to replace meals. We have more information about the different kinds of supplements and how they can help.

Try to keep active

It is important to try to keep active, even if you are losing weight. Without some activity, your muscles can get weak quickly. Activity should be done at your own pace. Gentle exercise, such as going for a short walk, may be all you need. Your doctor, nurse or physiotherapist can advise you on how much and which types of exercise would be helpful for you.

Getting help with meals

You may not always feel well enough to cook food for yourself or others. If you usually prepare meals for your family, it may feel strange to let someone else take charge. Try not to feel guilty about letting someone else do the things you usually do.

If you find ready meals or pre-prepared meals easier than cooking, use them on days when you do not feel like cooking.

If you live on your own and need help with cooking or shopping, contact your GP, district nurse or social worker. They may be able to arrange for a home helper, meals on wheels or a local organisation to help you with cooking or shopping.

If you are a carer

If you are the main carer for someone with cancer, it can be upsetting and difficult to know how to deal with eating problems, such as lack of appetite or weight loss. People who are ill often do not feel like eating.

The amount someone can eat may change each day, and their likes and dislikes may also change. Try not to put pressure on someone to eat. This can sometimes cause arguments. If you know when their appetite is at its best, you can make the most of it. For example, you could treat them to their favourite foods.

If the person you are caring for continues to struggle with food and is losing weight, speak to their doctor or nurse. They can refer them to a dietitian. The dietitian can advise on using nutritional supplement drinks if this is appropriate.

We have more tips about helping to build-up someones diet.

Your feelings about weight loss

Weight loss can be upsetting and difficult to cope with. This is because it can be a visible reminder of your illness. It can also affect your body image. Body image is the picture you have in your mind of how you look. It is how we think and feel about our bodies and how we believe others see us.

If you lose weight because of cancer or its treatment, you will see a different image of yourself from the one you are used to. You may find it hard to accept that you look different because you have lost weight. You may feel angry, anxious or sad. It is natural to feel like this. It is part of adapting to the way you see yourself. You may meet other people who have similar thoughts and feelings.

You may worry that the change in your appearance will affect relationships with a partner, family and friends. You may be anxious about what people think of you or about being rejected. Or you may feel self-conscious about eating at home or out with your family and friends.

Talking about how you feel

People often keep their thoughts and feelings about their bodies to themselves. But keeping your worries hidden can make them grow into something bigger. So, it is important to talk to someone.

Many people find it helps to talk to someone close to them. If you find it difficult to talk about your feelings with a partner, family member or a friend, you could talk to your doctor or specialist nurse. You may also find it helpful to speak to a counsellor. Your GP or nurse can give you advice on how to contact one.

If you are close to someone who has had physical changes, it may take you time to adjust and accept the changes. You may need to talk about your feelings too.

About our information

  • References

    Below is a sample of the sources used in our building-up diet information. If you would like more information about the sources we use, please contact us at

    European Society for Clinical Nutrition and Metabolism (ESPEN). ESPEN guidelines on nutrition in cancer patients. February 2017 [accessed Jan 2020] 

    European Society for Clinical Nutrition and Metabolism (ESPEN). ESPEN expert group recommendations for action against cancer related malnutrition. June 2017 [accessed Jan 2020] 

    World Cancer Research Fund (WCRF). Healthy living after cancer. 2016. [accessed Jan 2020]      

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Chief Medical Editor, Professor Tim Iveson, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 August 2020
Next review: 01 August 2023

This content is currently being reviewed. New information will be coming soon.

Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.