Back in 2002, the International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO) published findings that obesity is connected to increased risk of five types of cancer: colorectal, esophageal (adenocarcinoma), renal cell carcinoma, breast cancer in postmenopausal women, and uterine endometrial cancer.
New findings show eight more cancers have been identified at increased risk of occurrence due to obesity, bringing the total up to 13 types of cancer.
The added cancers are: stomach (gastric cardia area), liver, gall bladder, pancreas, ovarian, thyroid, meningioma and multiple myeloma.
The recent report is published in the August 25, 2016 issue of The New England Journal of Medicine and is based on a “review of more than 1,000 studies of excess weight and cancer risk analyzed by the World Health Organization’s International Agency for Cancer on Research (IARC).”(2)
In this new report, the risk has been rephrased as "the absence of excess body fatness reduces the risk of cancers," according to Medscape.
How increased fat amount contributes to development of cancer is not exactly known but there several possible mechanisms suggests the National Cancer Institute:(4)
1) Fat tissue causes excess estrogen to be produced. Increased amounts of estrogen have been found to increase the risk of breast and endometrial cancer.
2) Obese people often have increased levels of insulin, which may lead to tumor production.
3) Fat cells produce hormones that can affect cell production and growth.
4) Obese people are thought to have low levels of inflammation in their bodies, which may increase their cancer risk.
The studies used were observational studies so actual cause and effect cannot be drawn but the associations the researchers found suggest strong evidence that was not explained by other possible variables or bias.
It is natural to wonder if losing weight will reduce the risk of cancer.
1) Overweight/Obesity Linked to Eight More Cancers. Medscape Nurses. Retrieved August 26, 2016.
2) Excess weight linked to 8 more cancer types. Retrieved August 26, 2016.
3) Obesity Is Linked to at Least 13 Types of Cancer. Retrieved August 26, 2016.
4) Obesity and Cancer Risk. National Cancer Institute. Retrieved August 26, 2016.
5) Excess Weight Tied to Higher Risk for Many Cancers, Experts Say. Healthday News. Retrieved August 26, 2016.