Obesity/Overweight Link to Increased Cancer Risk

In that previous epidemiological studies indicate that overweight and obesity are associated with increased cancer risk, Michael Karin, from the University of California-San Diego (UCSD; California, USA), and colleagues studied a laboratory animal model of hepatocellular carcinoma (HCC), the common form of liver cancer whose occurrence and progression are the most strongly affected by obesity among all cancers.  The team found that obesity enhanced the development of HCC by stimulating the production of tumor-promoting cytokines – interleukin-6 (Il-6) and tumor necrosis factor (TNF) – that also cause chronic inflammation. Production of these signaling molecules, which are elevated in obese mice and in humans, causes inflammation of the liver and activation of a tumor-promoting transcription factor, a protein called STAT3. This protein in turn activates the formation and growth of liver cancer.  While the actual increase in cancer risk is dependent on the type of cancer and the body-mass-index (BMI),  the team estimates that the largest effect of BMI higher than 25 (the recommended BMI level) is seen on HCC, with the risk of this type of liver cancer increasing by up to 4.5-fold in men with a BMI of between 35 and 40. The researchers also warn that the effect of excess body weight increases the risk of all cancers, by an estimated 1.5-fold in men and 1.6-fold in women.