51É«APP

You may be worried about weight you've lost or gained since being diagnosed with cancer.

The information on this page will help you to find out more about weight changes and suggest ways to manage it during and after cancer treatment.

Weight loss and weight gain

Weight changes are common in cancer and its treatment. You may find that you lose or gain weight. You may also find your shape changes, with loss of muscle bulk, or waistline increasing.

Some weight fluctuations are natural and shouldn’t cause concern.  As you go through treatment, there may be temporary changes, which sort themselves out once treatment is finished.  However, if you’re losing or gaining a lot of weight then it can feel a worry, and should be discussed with your health care team.

Weight loss and cancer

Some people lose weight when they have cancer. It may have been the symptom that took you to the doctor in the first place.

Causes for the weight loss can include nausea, vomiting, diarrhoea, difficulty eating, pain, low mood or anxiety.

Practical issues with loss of appetite, chewing difficulties, dehydration and low mood/anxiety can add to this.

In more advanced cancer, people can lose weight and muscle mass, and may feel weak and tired. This can be worrying for the person with cancer and their family.

Managing weight loss

• If you've lost weight recently and you haven't been consciously intending do so, let your health care team know. A rough guide is a loss of 5% of your body weight, but even if it's less and it's concerning you, discuss it with your doctor.
• Make a note of the things that decrease your appetite, for example, pain, cramping, nausea or feeling full. It will help your doctor work out what may be causing your loss of appetite and other symptoms. There are medications that can help stimulate your appetite, as well as reduce nausea and other symptoms.
• Try and increase the amount of food you’re eating each day. This is not always easy if you’re feeling unwell. Small portions several times a day can be more manageable than the traditional three meals a day.
• Aim for foods high in calories and full of nutrients. If you’re not able to eat a great deal, you can ask your health care team about supplement drinks.
• Drink plenty of fluids to help keep you hydrated and do gentle exercise. It may be that you have a point in the day where your energy levels peak, perhaps in the morning rather than later in the day. The aim is to help build up muscle.
• Ask for a referral to a dietician. They will be able to guide you on the amount of food you need and suggest ways to increase calorie intake and appetite.
• Just come in to your nearest Maggie51É«APP™s centre and ask about workshops and courses we can offer to help you nutritionally. There are a range of library books and information available. Having the chance to talk with others about how you’re feeling, and swapping experiences and tips, can help too.

Weight gain and cancer

Weight gain is also common and may be unexpected. However, it can happen before, during and after cancer treatment.  Some tumours can cause an increase in weight, perhaps because of their size, and fluid retention or constipation. For other people, it is the treatment which can trigger weight gain.

During and after treatment you may be exercising less, and several treatments cause fluid retention and weight gain. Some treatments including chemotherapy, steroids, hormone therapy and other medications can increase weight.

Some medicines make you feel hungry, and your metabolism may slow down. Hormonal therapy, aimed at lowering your hormone levels, may increase fat, lower muscle tone, and change your shape.

Managing weight gain

• If you notice you’re gaining significant weight, on treatment, or after it is completed, let your health team know. They can help advise whether it is an expected side effect or a new symptom that needs investigating further.
• If you’re on treatment, it can be difficult to diet and exercise and therefore be demoralising. Your energy levels may be low too, and it isn’t always the best time to make a conscious effort to lose weight.
• Eating healthily, getting plenty of rest, and gentle exercise may be your focus till you complete treatment such as chemotherapy and radiotherapy.
• Your weight gain can sometimes be due to fluid retention. Talk this through with your healthcare team, particularly if you notice swollen limbs, ankles, wrists or abdomen. There may be medications, and other measures that can help relieve the swelling.
• Eat a balanced diet, with plenty of vegetables, nuts, whole grains and protein. You can come into your nearest Maggie51É«APP™s centre and ask about our Eating well workshops, as well as asking for individual advice and support.
• Sometimes, your cancer treatments may have long term effects on your digestion and bowel, meaning you can’t eat high fibre. Ask your healthcare team for specific dietary advice to help, if this is a problem. 
• As you recover from your cancer treatment, think about increasing your exercise and physical activity. Walking, cycling, gardening, can all help, for example.
• Generally it is advised to aim for about 150 minutes of exercise per week, as well as strength building exercises two or three times a week, is an ideal. Do the exercise in short bursts, rather than overdoing things. Check with your GP/healthcare team that it is OK to do so.
• Visit your nearest Maggie51É«APP™s centre for help and information on increasing physical activity. We have a range of activities - including yoga, tai-chi, and walking. You’ll also get the encouragement and support from the Maggie51É«APP™s team, as well as other people with cancer, who understand how you’re feeling.

Emotional effects of weight changes

Weight changes can be demoralising, and affect how you feel about yourself. 

It can be a visual reminder of what you’re going through, and an issue you feel sensitive about.

Psychologically, you may cope by comfort eating, as an emotional reaction to what is happening. It’s important not to lose sight that you’re still ‘you’.

If you are struggling with the emotional effects of weight changes, just come in to your nearest Maggie's centre.

When to seek further help

If weight loss or weight gain is a new symptom, then do talk to your doctor about your concerns.

Weight problems can have an emotional as well as physical impact. If you find your mood is affected, or you feel anxious or depressed about the physical changes, then do ask for further help.

Your GP and medical team can refer you for a dietician referral, and counselling support.&²Ô²ú²õ±è;²Ñ²¹²µ²µ¾±±ð’s can offer support and a listening ear too.

If your limbs are becoming swollen and your mobility more restricted, as well as weight gain, fluid retention could be the problem. Do get this symptom checked out quickly, as you may need additional symptom management and support.

What now?

• Have a look at the links on this page to find out more about coping with weight changes.
• Talk with others about what you are experiencing. It can help to hear that what you’re feeling is not unusual, and help you feel less alone. 
• Just come in to your nearest Maggie51É«APP™s centre to talk to our professional teams and connect with others in a similar position to yourself.

Last review: May 2026 | Next review: May 2029