Cancer weight loss

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on May 3, 2022.

The majority of cancer patients lose weight at some point in the course of the disease. Weight is sometimes the sign that leads someone to get diagnosed with cancer, but it may occur at any time, such as during treatment or in the advanced stages of the disease.

The patient's eating habits may change. Feelings of stress or worry may affect his or her ability to eat. If the cancer care team includes a dietitian, he or she can help patients find ways to keep weight on and stay strong.

Why does cancer cause weight loss?

What all types of cancer have in common are abnormal cells. These cancerous cells divide, proliferating and crowding out healthy cells—a process that taps into the body’s energy source, causing cancer patients to burn more calories at rest.

Between 31 percent and 87 percent of cancer patients say they experienced unexplained, unintentional weight loss. The weight change that precedes a cancer diagnosis is typically a loss of 10 pounds or more, and it most often occurs with cancers that affect the following areas:

Sometimes, this weight loss isn’t a direct result of the disease, but how it affects the patient's desire to eat (loss of appetite), eating habits and the way the body processes and absorbs food. These actions may lead to weight loss.

Appetite changes related to the disease itself may be brought on by:

  • A tumor (or tumors) in the abdominal area that interferes with digestion, stimulates a false sense of fullness, or makes swallowing food difficult.
  • Hormones produced by some types of tumors that alter the signaling process that tells the patient when he or she is hungry.
  • Any emotional or physical side effects of cancer—such as pain, stress, depression, dehydration and nausea—that diminish the patient's appetite.

Some types of cancer may make it difficult to swallow food, contributing to weight loss. This may be caused by:

  • Cancers that interfere with the communication channels between the brain and the esophagus (the brain tells the esophagus when to swallow), including some brain tumors or cancers that cause strokes or nervous system issues
  • Tumors in or near the esophagus that cause blockage

People who aren’t currently diagnosed with cancer but are worried that they may have cancer due to a recent loss of weight should know that fluctuations in weight are incredibly common and are usually nothing to worry about. However, speak with a doctor if the weight loss is:

  • Significant—more than 5 percent of body weight
  • Sudden—over the past few months
  • Continuous
  • Unintentional
  • Accompanied by fatigue, appetite loss, bowel changes or increased illness or infections

Weight loss associated with cancer treatment

Many of the common treatments used to fight cancer come with side effects that may interfere with the patient's desire to eat and make eating difficult or painful.

Such treatments include:

These therapies may lead to weight loss by causing side effects such as:

Managing weight loss with nutrition

Good nutrition is an essential component of combating cancer-related weight loss. While the patient may be used to eating a balanced diet with an emphasis on vegetables, fruits and whole grains, he or she may need to tweak this approach if the illness or its treatment has caused significant weight loss. This may help patients build up strength, return to a healthy weight, and ensure that the body is properly fueled with key nutrients.

Cancer patients may likely have unique nutritional needs, depending on factors such as the cancer type and stage, symptoms and treatment side effects, the amount of weight loss and any nutritional deficits that have occurred.

It may be helpful to:

  • Eat several smaller meals throughout the day, rather than three big ones
  • Set a schedule to eat to make sure the patient is getting enough calories
  • Eat high-protein and high-calorie foods such as peanut butter, oils, avocado, nuts and seeds
  • Top any foods with extras such as nut butters, jams, honey and mayonnaise
  • Make high-protein milkshakes, smoothies and soups. Use high-protein milks in food recipes

A registered dietitian specializing in oncology may design a personalized nutrition plan tailored to the patient's needs.

Medications to promote weight gain

The patient's doctor may recommend medicine to help him or her regain weight or prevent further weight loss, including:

  • Megestrol acetate: This hormone-based medication may help boost appetite and lead to weight gain.
  • Metoclopramide: This medication can ease nausea and vomiting, potentially leading to a higher likelihood of consuming more calories.
  • Dronabinol: This medication, in the cannabinoid category, may reduce nausea and vomiting so patients are likely to consume more.

What is cachexia?

If cancer-related weight loss is significant and accompanied by muscle loss, the patient may have a condition called cachexia or "wasting" syndrome. Cancer cachexia isn’t the kind of weight loss that may be easily thwarted by increasing calorie intake, as it’s caused by the body mistakenly breaking down muscle tissue and fat.

Cachexia is especially common in people with cancer that has widely metastasized, or spread throughout the body. It affects up to 80 percent of people with advanced cancer and contributes to about one-third of all cancer deaths. Cachexia is typically diagnosed in people who have:

  • Lost more than 5 percent of their body weight in the prior six months
  • Lost more than 2 percent of their body weight in a short time and have a body mass index (BMI) below 20
  • Experienced muscle loss in addition to weight loss of more than 2 percent

Alongside the significant fat and muscle loss, cachexia symptoms may also include severe fatigue and frailty. Patients with cachexia or severe malnourishment may need to have nutrients delivered through an intravenous (IV) tube.

Expert cancer care


CALL NOW: 855-680-1184