Weight Loss During Cancer Treatment

Weight loss is a common side effect of cancer and its treatment. It can be caused by reduced food intake, treatment side effects, inflammation or metabolic changes. Weight loss can occur through the loss of body fat, muscle, or a combination of both (1). The amount of weight you lose depends on your body composition, the type of cancer involved, the treatment you are receiving, and your overall activity level. It is normal to feel discouraged, worried, or exhausted when you notice unexpected weight loss; therefore, understanding why it happens and how you can deal with it can make things easier.

Weight loss during cancer treatment may not be obvious. Subtle changes you may notice include:

• Finding that your clothes don’t fit anymore, or your belt needs another notch.
• Comments by people close to you about your weight.
• A drastic change on the scales.
• Fatigue and low energy.
• Reduced appetite and feeling full too early.
• Loss of muscle mass and strength.

You need a doable strategy that is also easy to sustain as you manage weight loss related to cancer treatment. Here are some tips:

• Monitor your weight: get a bathroom scale and weigh yourself weekly.
• Avoid weighing more than once a week.
• Adjust your meals to ensure you’re getting enough nutrients between treatment cycles.
• Receive dietary counselling from a professional.
• Follow your medical team’s advice and take medical nutrition if recommended, under their medical supervision.

Exercise supports appetite, muscle health and recovery. Physical activity goes hand in hand with good nutrition. Keeping active may include doing as much as you can of your normal daily activities. For some this might be having the energy to shower, prepare a meal or snack, do some light housework or get out for a walk. For others this might be going for a cycle or swim; it’s all about what is normal for you. Being active can help you to feel more positive; try and make the most of your good days to get out and about.

You may need specific exercises and activities to support maintaining or building muscle or muscle strength.  Members of the healthcare team, including physiotherapists, may provide the specific advice you need. If you are considering taking on new forms of exercise or physical activity or joining a gym, speak to your healthcare team first.

You may sometimes feel saddened by how much weight you have lost. This is normal. Unplanned and unexplained loss can be frightening. It helps to understand that none of this is your fault, and there are ways to manage it.  Here are some helpful strategies:

• Focus on your strength and energy rather than achieving a specific weight.
• Focus on what your body can do rather than how it looks.
• Wear comfortable clothes that you feel confident in.
• Practice self-compassion and avoid negative self-talk about your body.
• Connect with people who have experienced similar challenges through support groups or patient communities.
• Share your concerns with trusted family members, friends, or healthcare providers.
• Seek counseling or therapy if feelings of sadness, anxiety, or frustration become overwhelming.
• Embrace stress-reducing activities such as meditation, deep breathing exercises, journaling, or gentle physical activity.
• Celebrate small victories and focus on things that create meaning, enjoyment, and a sense of control.

As a caregiver, you can help someone who is losing weight from cancer treatment by:

Supporting them to eat well. A few ways to do this include:

• Offer small, frequent meals and snacks throughout the day.
• Serve their favourite foods whenever possible, even outside traditional mealtimes.
• Make high-calorie, high-protein snacks readily available.
• Mash or blend food if eating is difficult.
• Provide nutrient-rich drinks such as smoothies or milkshakes.
• Make mealtimes pleasant by eating together and creating a relaxed atmosphere.
• Ask what they want to eat rather than insisting on specific meals.
• Avoid pressuring, nagging, or arguing about food intake, which can increase stress and reduce appetite.
• Accommodate changes in taste and food preferences by offering options.

Help monitor their weight:

• Track weight regularly using the same scale and similar conditions.
• Keep a record of weight changes and share concerns with the healthcare team.
• Monitor for signs of poor nutrition, such as muscle loss, weakness, fatigue, or loose clothing.
• Maintain a food diary if recommended by the healthcare team.
• Report significant or rapid weight loss to a healthcare provider promptly.

Provide emotional support:

• Listen without judgment when they express concerns about weight loss or changes in appearance.
• Acknowledge their worries, frustrations, or concerns and reassure them that their worth extends beyond their appearance.
• Help them stay connected with friends, family, and support groups.
• Celebrate small successes, such as finishing a meal or maintaining weight.
• Encourage activities that promote confidence, comfort, and enjoyment.
• Support them in seeking professional counseling if they experience significant anxiety, depression, or body image concerns.
• Be patient and understanding, recognizing that appetite and eating habits may fluctuate throughout treatment.

Talk to your healthcare team about concerns with eating and drinking or weight loss. Some symptoms that interfere with eating and drinking can be managed with medication and others through dietary changes or a combination. And remember, some days, such as when you are particularly tired or in the week after chemotherapy, may be worse than others. 

Speak to your care team immediately if you notice any of these symptoms:

• Unintentional weight loss, especially if you’ve lost around 5% or more of your body weight over the past few months.
• Persistent loss of appetite that makes it difficult to eat.
• Difficulty chewing, swallowing, or keeping food down due to nausea, vomiting, or mouth sores.
• Severe fatigue or weakness that interferes with daily activities.
• Muscle loss or difficulty performing previously manageable tasks.
• Dehydration (e.g., dizziness, dark urine, dry mouth, or reduced urination).
• Ongoing digestive problems that affect food intake, including vomiting, diarrhoea, constipation, or abdominal pain.
• Emotional distress, anxiety, depression, or body image concerns related to weight loss.

Weight loss during cancer treatment is common and often caused by the cancer itself, treatment side effects, and reduced appetite or taste changes. Early nutritional support, including dietary changes and medical nutrition when recommended by your doctor/medical team, can help prevent further decline and maintain strength. Guidance from your medical team helps manage symptoms and personalise care. Emotional and practical support from your caregiver, support groups, friends, and family can also improve your well-being and quality of life.