If you have colon cancer, you may find that certain complications and even treatment can cause bloating and weight gain.

Colon cancer is cancer in the longest part of the large intestine. Common symptoms usually include a consistent and uncomfortable change in bowel habits. These changes can result in bloating, excessive gas, cramping, and abdominal pain.

Colon cancer can also cause fluids to build up in the abdominal area, which can contribute to weight gain and bloating.

Certain treatments for colon cancer, such as chemotherapy and steroids, can also lead to weight gain.

In this article, we take a closer look at how colon cancer causes bloating and weight gain.

Colon cancer causes disturbances in the gastrointestinal (GI) tract, which can lead to prolonged changes in bowel habits. The resulting digestive issues, such as constipation, diarrhea, and abdominal cramping, can lead to bloating and possibly weight gain.

Other ways that colon cancer can cause bloating or weight gain include:

  • Fluid retention: Buildup of fluid in the abdominal area (a condition called ascites) can be caused by tumor growth, medications, or an electrolyte imbalance. This is usually seen in more advanced cancers.
  • Chemotherapy: Chemotherapy drugs may cause weight gain by altering metabolism, increasing appetite, and causing fluid retention.
  • Steroid medications: Steroid therapy may be used in colon cancer treatment to reduce inflammation or manage cancer symptoms. Weight gain is a common side effect of these medications and is known to increase appetite.
  • Hormonal changes: Some colon cancers produce hormones that can affect the metabolism and contribute to weight gain.
  • Inactivity: Fatigue is common in colon cancer. It can result in more sedentary behavior.
  • Stress: Stress can create hormonal changes in the body, leading to weight gain.

In addition to bloating, other symptoms of colon cancer include:

These symptoms alone don’t mean you have colon cancer. However, if you experience any of them for more than a few days, check in with a doctor.

There’s no single cause for colon cancer, but certain factors and habits may increase your risk.

The primary risk factors for colon cancer include:

  • Obesity: A higher BMI is associated with a higher risk of colon cancer.
  • Inactivity: Less active people are at higher colon cancer risk.
  • Diet: Diets high in salt and saturated fats are linked to colon cancer.
  • Smoking: Smoking, including secondhand smoke, can increase your colon cancer risk.
  • Age: People over age 50 are at a higher risk.
  • Family history: Colon cancer occurs in people without any family history, but 1 in 3 people with colon cancer have a family member who has had it.
  • Inflammatory bowel disease: If you have a history of IBD or Crohn’s disease, it’s a good idea to be screened for colon cancer at a younger age.
  • Excess alcohol consumption: Moderate to heavy alcohol use has been linked to colon cancer.

Can having obesity put you at risk for colon cancer?

There’s consistent evidence to show that obesity is a contributing risk factor for colon and several other cancers. Colon cancer is 1.3 times more likely in people with obesity than in those without obesity.

A recent study determined that women with a BMI over 30 were more than twice as likely to be diagnosed with early-onset colon cancer than women with a BMI range of 18.5–22.9.

While it’s not known whether obesity is an actual cause of colon cancer, it has been determined to be a leading risk factor. This may be because people with obesity may differ from others in more ways than body fat. Obesity is associated with various chronic health conditions, all of which can increase your risk for colon and other cancers.

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Cancers that are most likely to cause weight gain include any cancers that affect your body’s hormones. While weight gain and swelling may not be caused by the cancer itself, it can also be a common effect of some treatments.

The cancers that may cause weight gain either as a symptom or a result of treatment include:

Colon cancer can cause digestive issues such as constipation, diarrhea, abdominal cramping and nausea. These digestive issues may lead to bloating and weight gain.

Bloating during colon cancer can also be the result of fluid buildup in the abdominal area.

Weight gain is not often caused directly by colon cancer, but is more likely the result of cancer treatments. Chemotherapy and other cancer medications, such as steroids, have been known to cause weight gain in people with colon cancer.

If you are experiencing bloating and weight gain as a result of colon cancer, work with your doctor on ways to minimize these issues.