Obesity and Liver Cancer in Japan: A Comprehensive Review

Lifestyle-related factors play a major role in the development of cancer. In recent years, obesity has become widespread in the world and has attracted attention not only as a cause of diabetes mellitus and atherosclerotic diseases but also as a factor in carcinogenesis. In Japan, the number of obesity-related malignancies has been increasing with the westernization of lifestyle. On the other hand, it is estimated that there are more than 10 million nonalcoholic fatty liver disease (NAFLD) patients in Japan. NAFLD is classified into simple fatty liver and nonalcoholic steatohepatitis (NASH), and 10-20% of NASH patients will progress to liver cirrhosis and 2-3% of them will develop hepatocellular carcinoma (HCC) per year. Research interest in metabolism-associated liver cancer has been increasing in recent years. Here in this review, we will comprehensively summarize the current knowledge with regard to the relationship between obesity and HCC in Japan.