Weight loss

People with cancer may lose weight without meaning to during their cancer experience. Weight loss can be a sign of cancer or be caused by a side effect of treatment. Side effects such as nausea and vomiting and loss of appetite can make eating difficult and cause weight loss.

Dealing with unintentional weight loss can be challenging, but it is normal for many people with cancer. If you are losing a lot of weight, talk to your doctor or someone on your healthcare team. They can refer you to a dietitian to minimize or prevent further weight loss. A dietitian can also make sure you are getting enough nutrients during treatment.

When you have cancer, you may lose weight for many reasons. Weight loss is often the result of certain side effects of treatment, but it may also be caused by the cancer itself.

Certain types of cancer can affect your ability to eat. Some cancers can make you feel full or make eating painful because of sores in your mouth or throat. Some types of cancer can also make it harder for your body to absorb nutrients (called malabsorption).

Weight loss may be more common in lung cancer and upper gastrointestinal cancers such as pancreatic, stomach and esophageal cancer.

Cancer can change how your body uses nutrients and make your metabolism burn calories too quickly. This can result in a drastic loss of fat and muscle mass called cancer cachexia or wasting syndrome. Cancer cachexia is more common in advanced cancer.

Cancer treatments including surgery, chemotherapy, targeted therapy, immunotherapy and radiation therapy may have side effects that affect your appetite or ability to eat. These include:

• nausea and vomiting

• difficulty chewing and swallowing

• constipation or diarrhea

• anxiety or depression

Side effects like diarrhea or vomiting can also cause dehydration. When you are dehydrated, you lose more fluids than you take in and you may lose weight.

Signs and symptoms of weight loss include:

• lack of appetite

• low red blood cells (anemia)

• weakness and fatigue
• looking thin or frail, or clothes no longer fitting properly
• dizziness
• weakened immune system

Once your healthcare team knows the cause of your weight loss, they can suggest ways to manage it. You can also try the following tips to help you gain weight.

• Increase how often you eat in a day. For example, instead of eating 3 large meals, try eating small meals every 2 to 3 hours or aiming for 5 to 6 small meals per day.

• Drink high-calorie beverages, such as oral nutrition supplement drinks (often pre-made protein shakes) or a homemade smoothie.
• Eat foods high in calories, protein and fat, such as yogurt, avocado and nuts.
• Drink liquids between meals instead of with meals so they don't fill up the stomach at mealtime.
• Avoid foods that can cause bloating, such as beans, broccoli, corn, cabbage, and cauliflower. Carbonated drinks and chewing gum can also cause bloating and should be avoided.
• Ask your healthcare team to refer you to a registered dietitian.

You may be offered medications to treat severe weight loss. This depends on your specific situation.

If you are losing a lot of weight and have difficulty eating or drinking, your healthcare team may suggest tube feeding or intravenous (IV) nutrition. Tube feeding or IV nutrition may be used if you:

• can't absorb nutrients properly or need more nutrition, including protein and calories
• are having swallowing problems
• can't eat or drink during or after cancer treatment
• have an extremely sore mouth and throat

Find out more about eating well when you have cancer.