[Obesity and cancer]

Obesity which is now well recognized as a public health problem increases the risk of developing cancers. Some systematic review and meta-analyses assessed the strength of associations between body mass index and common cancers such as breast, endometrial, colon and adenocarcinoma of oesophagus. The causal mechanisms remain unexplained. However, epidemiological data and animal models have provided some evidence that hormonal alteration linked to obesity, such as hyperinsulinism, high insulin-like growth factor (IGF-1) levels or biodisponibility, low adiponectin serum level and high oestradiol serum level resulting from an enhanced aromatase activity may have mitogenic and antiapoptotic effects. The inflammation associated with visceral adiposity is another factor which promotes cancer. To date, there are no convincing data that weight loss could improve the prognosis of treated neoplasia. However, a regular physical activity and a limited caloric intake are probably safe in healthy subject to prevent cancer and also in cancer survivors.