Abstract

For more than two decades, an increased interest in understanding relationship between obesity and cancer is observed in the medical literature. However, epidemiological data remain heterogeneous depending on cancer site, age, gender, type of tissue adipose (visceral, subcutaneous) and ethnicity: obesity is linked with a greater risk of colo-rectal cancer (CRC) for men of all ages and for premenopausal women. Mechanisms involved are not fully investigated: no specific genetic marker linking obesity and cancer is identified, and except for few metabolic markers, pathways in this field remain speculative. Effects of hormones are more investigated. Insulin is the best established biochemical mediator between obesity and CRC and insulin resistance is important in the pathogenesis of CRC. Leptin, a very well known hormone that regulates food intake and energy balance is reported as tumorigenic mediator to explain why polyps are over expressed in obese individuals, however it may influence also anti tumoral immune response. Regular exercise is identified to reduce the risk of developing CRC. We should consider exercise, obesity and anti tumor immune response when designing colon cancer screening protocols.