Have you noticed a decrease in your body weight after being diagnosed with kidney cancer? Maybe the weight change became more noticeable after you started cancer treatment.

These experiences are common in people with kidney cancer who are receiving kidney cancer treatments. In a survey of people with renal cell carcinoma (RCC), which is the most common type of kidney cancer in adults, almost half of the participants said they’d lost weight unintentionally.

There are multiple reasons why unintentional weight loss often occurs in people living with kidney cancer. In this article, we’ll go over a few of the most common kidney cancer-related reasons for weight loss and causes of weight loss related to kidney cancer treatments.

Kidney Cancer-Related Causes of Weight Loss

Although kidney cancer often doesn’t cause symptoms in the early stages, unexplained weight loss and other kidney cancer symptoms might become noticeable as time goes on. Without factoring in cancer treatments, kidney cancer by itself can cause weight loss because of various changes that occur inside your body.

1. Cancer Cachexia

Cancer cachexia is a metabolic change that cancer can cause. It affects up to 75 percent of people with later-stage cancers. Cancer cachexia is a type of wasting syndrome, which means it involves losing both body fat and muscle.

Your doctor may determine you have cancer cachexia related to kidney cancer if you lose more than 10 percent of your body weight in a six- to 12-month period.

Cancer cachexia occurs because cancer speeds up your metabolism, which makes it harder to eat enough food to meet your body’s metabolic needs. Several events inside your body cause this metabolic change, including chemical changes that cause inflammation. Cancer tumors themselves cause inflammation too.

This inflammation makes you lose fat and muscle faster than you would without it. Cancer cachexia can also occur when cancer causes proteins to break down faster than your body can replace them. A faster protein turnover leads to muscle loss, which can impact your body weight.

2. Appetite Loss

Kidney cancer can make it so you have very little appetite. In the survey of people with RCC, over 21 percent of participants said they noticed a decreased appetite.

Often appetite changes are linked to the pain that cancer causes. When you’re in pain, you’re less likely to feel hungry and focus on food. Your appetite can also change when cancer-related inflammation alters the hormones that stimulate your appetite and make you feel hungry.

A smaller appetite means less eating, so you may lose weight from eating less. A significant loss of appetite can be one of the key signs of kidney cancer.

3. Constipation

Kidney cancer can cause constipation if kidney tumors grow large enough to block the movement of stool through your gastrointestinal (GI) tract. Additionally, imbalances in electrolytes such as calcium and potassium can make it harder to have bowel movements. You may also get less physical activity due to cancer-related fatigue, leading to slower GI movement.

When you’re constantly constipated, you may feel full all the time and lose the desire to eat. For some people, constipation can lead to nausea and vomiting, which can also contribute to unintentional weight loss.

4. Emotional Distress

Being diagnosed with kidney cancer, as well as the ups and downs of living with kidney cancer, can lead to emotional distress. In one study on the mental health of people with kidney cancer, over 90 percent of participants experienced anxiety symptoms, while over 87 percent showed signs of depression.

Both depression and anxiety can lead to appetite changes, causing you to eat either more or less than you normally do. You might eat fewer calories and lose weight as a result.

Anxiety can also cause symptoms like muscle tension and diarrhea, which can contribute to weight loss on their own. Muscle tension and movements can burn calories, while diarrhea can cause you to lose water and nutrients.

Kidney Cancer Treatment-Related Causes of Weight Loss

Weight loss in people with kidney cancer can also be attributed to common cancer treatments. Altogether, unintentional weight loss often happens from a combination of features of the cancer itself and treatment-related body changes.

1. Nausea and Vomiting

Nausea and vomiting can happen with certain kidney cancer treatments. These side effects are rarely linked to targeted therapy, immunotherapy, and radiation therapy. Traditional chemotherapy, commonly associated with nausea and vomiting, is not usually indicated for the most common kidney cancer (renal cell carcinoma), but it may be used for some less common kidney cancer types.

These side effects are typically most severe in people who receive multiple cancer treatments at the same time or who receive certain types of chemotherapy at high doses.

When you have trouble keeping food down because of nausea, you may have a hard time meeting your body’s caloric needs. If your treatment-related nausea prevents you from eating enough and causes significant weight loss, your doctor may prescribe an antiemetic to reduce these treatment side effects.

2. Chronic Diarrhea

Cancer treatments may also cause chronic diarrhea as a side effect, which can be a major contributor to unintended weight loss. You may experience diarrhea after a nephrectomy to remove part or all of your kidney.

Diarrhea is also a possible side effect of radiation therapy, immunotherapy, targeted therapies, and some types of chemotherapy. It can become an even greater issue if stress or anxiety causes diarrhea for you too.

3. Mouth and Throat Sores

Certain cancer treatments can irritate the lining of the mouth and throat and cause mucositis (inflammation of the lining of the mouth and throat) and painful sores. As a result, you may not eat as much.

Mouth and throat sores are common with certain chemotherapy medicines and with radiation aimed near the head, neck, or throat area. Radiation aimed at the kidney area, which is rarely indicated, is less likely to cause mouth or throat sores.

There are steps you can take to prevent mouth and throat sores while undergoing chemotherapy or radiation. Talk to your doctor about how to take good care of your mouth during kidney cancer treatment.

When To Talk to Your Doctor

Unexpected and unintentional weight loss is very common in people with kidney cancer, and it can result from losing both body fat and muscle. Fortunately, there are ways to manage treatment side effects, improve your nutrition, eat more of certain foods, and minimize unintentional weight loss while living with kidney cancer.

Tell your healthcare provider if you lose more than 5 percent of your body weight in a year or less without trying. It’s especially important to report weight loss with other possible kidney cancer symptoms, such as blood in your urine or lower back pain, that impact your quality of life.

Be sure to also tell your cancer care team about any treatment side effects you notice that make it more difficult to eat or other side effects associated with weight loss, like persistent diarrhea.

Too much unintentional weight loss can interfere with cancer treatments or make it unsafe to continue. Your healthcare team can offer tips or medications to help you tolerate kidney cancer treatment side effects and stay at a healthy weight.

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