Understanding How Overweight and Obesity Increases Cancer Risk

Being overweight or obese is linked to an overall increased risk of cancer. According to research from the American Cancer Society, excess body weight is thought to be responsible for about 8% of all cancers in the United States, as well as about 7% of all cancer deaths. 

Being overweight or obese is clearly linked with an increased risk of many types of cancer, including cancers of the breast (in women past menopause), colon, rectum, endometrium (lining of the uterus), esophagus, kidney, pancreas.  Studies show that being overweight or obese might also raise the risk of other cancers, such as gallbladder, liver, Non-Hodgkin lymphoma, multiple myeloma, cervix, ovary and aggressive forms of prostate cancer.

In addition, having too much belly fat (that is, a larger waistline), regardless of body weight, is linked with an increased risk of colon and rectal cancer, and is probably linked to a higher risk of cancers of the pancreas, endometrium, and breast cancer (in women past menopause).

But the links between body weight and cancer are complex and are not yet fully understood. For example, while studies have found that excess weight is linked with an increased risk of breast cancer in women after menopause, it does not seem to increase the risk of breast cancer before menopause. The reasons for this are not clear.

The timing of weight gain might also affect cancer risk. Being overweight during childhood and young adulthood might be more of a risk factor than gaining weight later in life for some cancers. For example, some research suggests that women who are overweight as teenagers (but not those who gain weight as adults) may be at higher risk for developing ovarian cancer before menopause.

Excess body weight may affect cancer risk through a number of mechanisms, some of which might be specific to certain cancer types. Excess body fat might affect:

• Immune system function and inflammation
• Levels of certain hormones, such as insulin
• Factors that regulate cell growth, such as insulin-like growth factor-1 (IGF-1)
• Proteins that influence how the body uses certain hormones, such as sex hormone-binding globulin

There is still much to learn about the link between weight loss and cancer risk.  It is becoming more and more clear that the benefits of weight loss are far reaching as scientific evidence continues to mount.  Aside from reducing cancer risk, losing weight can have many other health benefits, such as lowering the risk of heart disease, diabetes, arthritis and dementia.