One factor is linked with increased risk of 13 types of cancer, according to the Centers for Disease Control and Prevention (CDC). And those types of cancer account for around 40% of all cancer diagnoses in the United States. While the rate of new diagnoses of cancer has declined over the past two decades, the rate of diagnoses for the types of cancer associated with this factor have increased. 

What is this factor? Being overweight or obese. There's good news, though. You can lose weight to lower your risk for these cancer types.

A pair of bare feet stand on a bathroom scale, with a twisted yellow tape measure lying in the foreground.

Image source: Getty Images.

Types of cancer linked to weight

It might be surprising that so many types of cancer are linked to being overweight or obese. What are these cancer types? Starting at the top (literally) is meningioma, a cancer in the tissue covering the brain and spinal cord. Moving to the gastrointestinal tract and digestive system, esophageal adenocarcinoma, upper stomach cancer, gallbladder cancer, liver cancer, pancreatic cancer, and colorectal cancer all have been found to be associated with high weight levels.

In addition, people who are overweight or obese have higher risks for kidney and thyroid cancer. That's also the case for multiple myeloma, a cancer affecting blood cells.

The CDC's research found that 55% of all cancers diagnosed in women are associated with being overweight or obese, compared with only 24% for men. Several of the weight-related types of cancer are specific to women: postmenopausal breast cancer, ovarian cancer, and endometrial cancer, a cancer of the uterine lining. 

All of the bad statistics could have been even worse. The CDC noted that "screening for colorectal cancer prevents new cases by finding abnormal growths in the colon and rectum before they turn into cancer." Without this screening, more weight-related cancer diagnoses could have occurred.

Why weight matters

So why does weight matter when it comes to risk for cancer? There are several theories that could at least partially explain the linkage.

Obese people frequently experience chronic inflammation that can eventually cause DNA damage, which then leads to cancer. For example, inflammation resulting from gastroesophageal reflux disease (GERD) or Barrett's esophagus, a serious complication of GERD, is a probable cause of esophageal adenocarcinoma.

For women, fat tissue can produce excess levels of estrogen. These high levels have been associated with increased risks of breast, endometrial, ovarian, and other cancers. In both women and men, fat cells produce hormones that can affect cell growth. One such hormone, leptin, appears to promote cell proliferation -- which helps cancer spread.

But can reducing weight levels actually help reduce the risk of cancer? Oncologist Lisa C. Richardson, director of the CDC's Division of Cancer Prevention and Control, says, "Yes, good health is the best prescription for preventing chronic diseases, including cancer." Some studies have also found evidence of lower cancer risk following weight loss.

A gold mine?

If you knew of a company with a product that could help reduce the risks of 13 types of cancer, you'd probably think you had found a gold mine. The problem with gold mines, though, is that sometimes they don't contain much gold.

Arena Pharmaceuticals (NASDAQ:ARNA), for example, gained FDA approval for weight-loss drug Belviq in 2012. However, Belviq hasn't been a big winner in the market. Arena's stock performance now hinges more on its pipeline candidates.

On the other hand, Weight Watchers International (NYSE:WTW) stock has quadrupled this year. The company has taken several steps to appeal to customers, including enhancing digital offerings and updating its program. As a result, Weight Watchers' subscriber count at the end of the second quarter jumped 20% year over year to 3.5 million. 

The connection between weight and higher risks of diabetes has been known for a while -- but the upward trend for Americans diagnosed with diabetes hasn't slowed down. Will the latest report from the CDC make any difference? Maybe not. But it presents yet another marketing opportunity for companies like Weight Watchers. And look for health insurers to step up efforts to cajole members to lose weight, especially with the skyrocketing costs of cancer drugs. The old saying we've all heard might be more true than you thought: An ounce of prevention really could be worth a pound of cure. 

Keith Speights has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.