Obesity and Colorectal Cancer

Obesity worldwide is constantly increasing. Obesity acts as an independent significant risk factor for malignant tumors of various organs including colorectal cancer. Visceral adipose tissue is physiologically more important than subcutaneous adipose tissue. The relative risk of colorectal cancer of obese patients is about 1.5 times higher than the normal-weight individuals, and obesity is also associated with premalignant colorectal adenoma. The colorectal cancer incidence of obese patients has gender-specific and site-specific characteristics that it is higher in men than women and in the colon than rectum. Obesity acts as a risk factor of colorectal carcinogenesis by several mechanisms. Isulin, insulin-like growth factor, leptin, adiponectin, microbiome, and cytokines of chronic inflammation etc. have been understood as its potential mechanisms. In addition, obesity in patients with colorectal cancer negatively affects the disease progression and response of chemotherapy. Although the evidence is not clear yet, there are some reports that weight loss as well as life-modification such as dietary change and physical activity can reduce the risk of colorectal cancer. It is very important knowledge in the point that obesity is a potentially modifiable risk factor that can alter the incidence and outcome of the colorectal cancer.