The risk of illness in numerous types of cancer is increased by being overweight
The International Cancer Research Agency (IARC) of the World Health Organization has found in a current study to update the "Handbook of Cancer Prevention" that being overweight with significantly more forms of cancer than previously assumed increases the risk of illness. An association with obesity has been confirmed in eight other cancers, the IARC said.
According to the latest results from an IARC working group, obesity is a risk factor for more cancers than previously thought. IARC reports that it was already known that obesity is associated with an increased risk of colon, rectum, esophageal (adenocarcinoma), kidney, breast and uterine cancer. A connection between the risk of disease and existing overweight has now been demonstrated for eight other cancers.
More than 1,000 studies evaluated
The IARC working group of 21 independent international experts, in which Professor Rudolf Kaaks from the German Cancer Research Center (DKFZ) was also involved, has carried out a systematic review of the available scientific literature and published the results in the "New England Journal of Medicine". The researchers evaluated more than 1,000 studies, including intervention studies, cohort and case-control studies, studies on experimental animals and studies on the mechanisms of the link between excess body fat and cancer. In their investigation, they were able to confirm the already known increases in cancer risk in the aforementioned types of cancer. They also found a connection with cancer of the cardia (transition between the stomach and esophagus), the liver, gallbladder, pancreas and the thyroid gland. The risk of meningioma (brain tumors), multiple myeloma (cancer in the hematopoietic system) and ovarian cancer was also increased.
Maintain normal weight to avoid cancer
Overall, people with normal weight show a significantly lower risk of cancer than those who are overweight, and the current assessment clearly speaks for keeping their body weight as normal as possible in order to reduce the risk of different types of cancer, Dr. Béatrice Lauby-Secretan, lead author of the current review. "The new evidence shows how important it is to find effective ways to improve nutrition and physical activity patterns at the individual and societal level to address cancer and other non-communicable diseases," added the IARC director Dr. Christopher Wild.
Five percent of all cancers are attributed to obesity
"Overall, the data from the studies we evaluated indicate a relationship between dose and effect: the more pronounced obesity is, the higher the risk of cancer," reports Professor Kaaks in a press release from the DKFZ. In economically highly developed countries, overweight is estimated to account for five percent of the risk of developing all types of cancer. This would be an estimated 25,000 cases in Germany alone. In individual cancers, such as uterine and kidney cancer or adenocarcinoma of the esophagus, almost half of all cases are caused by obesity. "And the number of people affected will continue to increase because people around the world are still gaining weight," said Kaaks.
Causes of the connection have not been finally clarified
With regard to possible biological causes for the connection between being overweight and cancer, Professor Kaaks explains that the clearest indications are available for sex hormones and for inflammatory messengers that are produced by the adipose tissue. “Today we know very well that inflammation is a cancer accelerator. Sex hormones act on many cells as growth factors that drive cancer growth, ”says Kaaks. In the case of overweight people, increased amounts of the growth factor IGF (“insulin-like growth factor”), which also drives cell growth, can also be detected. The biological basis of the relationship has not yet been finally clarified. (fp)