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Obesity and Cancer Risk

Obesity has been shown to lead to an increased risk for many types of cancer. Several possible explanations for this association have been proposed, including:

  • Excess amounts of estrogen are produced from fat tissue. When high levels of estrogen are present, they can be linked with an increased risk of breast, endometrial, and other cancers.
  • Obesity often produces an increase in levels of insulin and insulin-like growth factor-1, called IGF-1, in the blood. This increased production may result in the development of certain tumors.
  • Adipokines are hormones that affect cell growth. Because they are produced by fat cells, this abnormal cell growth is more common in obese people.
  • Tumor growth regulators in the body are possibly affected, both directly and indirectly, by fat cells. This can increase the risk of tumors.
  • Chronic low-level inflammation, which has been linked to increased cancer risk, is often found in obese people, and
  • Immune responses, effects on the nuclear factor kappa beta system, and oxidative stress are mechanisms that may be affected by obesity, and can increase cancer risk.

Cancers Linked to Obesity

 

Many studies have demonstrated that specific types of cancer have been linked to obesity. These types of cancer include[1]:

  1. Breast Cancer
    The risk of postmenopausal breast cancer has been shown to rise in women who are obese. When the ovaries stop producing estrogen after menopause, the most important source of this hormone becomes fat tissues. These higher levels of estrogen can potentially lead to more rapid growth of estrogen-responsive breast tumors.

  2. Endometrial Cancer
    Although we do not know why obesity has been linked to cancer in the lining of the uterus, obese and overweight women are two to four times more likely to develop endometrial cancer, regardless of whether they are pre- or postmenopausal.

  3. Colorectal Cancer
    Higher BMI and increased waist circumference in men have been associated with colorectal cancer. It is not certain why, though there seems to be a link with being obese in the abdominal area. This connection can also be seen in obese women, though it is weaker.

  4. Kidney Cancer
    The most common form of kidney cancer is renal cancer, which has been consistently associated with obesity, both in men and women. The specific mechanism, however, is not understood.

  5. Esophageal Cancer
    Overweight and obese people are almost twice as likely as people of healthy weight to develop a cancer of the esophagus called esophageal adenocarcinoma. The mechanisms are not well-understood; however, an increased risk of this type of cancer has been associated with gastroesophageal reflux disease or Barrett’s esophagus, which is more common in obese people.

  6. Pancreatic Cancer
    A slight increase in risk of pancreatic cancer has been linked to obesity.

  7. Thyroid Cancer
    Excess weight has been shown to have an association with thyroid cancer, though it is not clear why.

  8. Gallbladder Cancer
    Though the reasons are not known, there is a correspondence between a rise in BMI and a rise in the risk of gallbladder cancer.

  9. Other Cancers
    Though the studies are not conclusive, possible links have been shown between obesity and prostate cancer, ovarian cancer, and liver cancer.

[1] “Obesity and Cancer Risk,” National Cancer Institute, http://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet, accessed July 7, 2016.