Does body weight affect cancer risk?
An estimated 1 out of every 3 cancer deaths in the United States is linked to excess body weight, poor nutrition, and/or physical inactivity. These factors are all related and may all contribute to cancer risk, but body weight seems to have the strongest evidence linking it to cancer. Excess body weight contributes to as many as 1 out of 5 of all cancer-related deaths.
Being overweight or obese is clearly linked with an increased risk of many cancers, including cancers of the:
Breast (in women post menopause)
Colon and rectum
Endometrium (lining of the uterus)
Being overweight or obese also likely raises the risk of other cancers, such as:
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.
Clearly, more research is needed to better define the links between body weight and cancer.