WHO overweight increases the risk of many cancers

Disease risk in numerous cancers increased by overweight
The World Health Organization's International Agency for Research on Cancer (IARC) has found in a recent study updating the "Handbook on Cancer Prevention" that overweight in significantly more cancers than previously thought increases disease risk. For eight other cancers, an association with overweight was confirmed, according to the IARC release.

Obesity is a risk factor for more cancers than previously thought, according to recent results from a IARC working group. It was already known that obesity is associated with an increased risk of colorectal, rectal, esophageal (adenocarcinoma), kidney, breast and uterine cancer, reports the IARC. Now it was possible to establish a connection between the disease risk and existing overweight for eight other cancers.

Obese people have a significantly higher disease risk in many cancers. (Image: yahyaikiz / fotolia.com)

More than 1,000 studies evaluated
The IARC working group of 21 independent international experts, which also involved Professor Rudolf Kaaks of the German Cancer Research Center (DKFZ), has carried out a systematic review of the available scientific literature and published the results in the "New England Journal of Medicine". The researchers have evaluated more than 1,000 studies, including intervention studies, cohort and case-control studies, studies in experimental animals and studies on the mechanism of the linkage between excess body fat and cancer. They were able to confirm in their study the already known increases in cancer risk in the types of cancer. In addition, they found a connection with cancers of the cardia (transition between the stomach and esophagus), the liver, gallbladder, pancreas and the thyroid gland. In addition, the risk of meningioma (brain tumors), multiple myeloma (cancer in the hematopoietic system) and ovarian cancer was also increased.

Keep normal weight to avoid cancer
Overall, normal weight people have a significantly lower risk of cancer than overweight and the current review clearly argues for keeping as normal a body weight as possible to reduce the risk of different types of cancer, said Dr. med. Béatrice Lauby-Secretan, lead author of the current review. "The new evidence highlights the importance of finding effective pathways at the individual and societal level to improve diet and physical activity patterns when addressing the burden of cancer and other noncommunicable diseases," adds the IARC Director Dr. Christopher Wild.

Five percent of all cancers attributed to obesity
"Altogether, the data of the studies evaluated by us point to a correlation of dose and effect: The more pronounced the obesity, the higher the cancer risk," reports Professor Kaaks in a press release of the DKFZ. Being overweight in the economically advanced countries is estimated to account for five percent of the disease risk of all cancers. This would be an estimated 25,000 cases in Germany alone. In individual cancers such as uterine and kidney cancer or adenocarcinomas of the esophagus, almost half of all cases are caused by obesity. "And the number of people affected will continue to increase as people around the world are still gaining weight," said Kaaks.

Causes of the connection are not finally clarified
Referring to possible biological causes of obesity-to-cancer relationships, Professor Kaaks explains that the strongest evidence exists for sex hormones and inflammatory mediators produced by adipose tissue. "That inflammation is a cancer accelerator, you know today very well. Sex hormones act on many cells as growth factors that drive cancer growth, "says Kaaks. In obese people, moreover, increased amounts of the growth factor IGF ("insulin-like growth factor") can be detected, which also drives cell growth. However, the biological basis of the relationship has not yet been finally clarified. (Fp)