There is growing scientific evidence that overweight and obesity are associated with increased risk of cancer. So far, there is convincing evidence from epidemiological studies that obesity is associated with a higher risk of colorectal cancer, postmenopausal breast cancer, endometrial cancer, renal cell cancer, esophageal adenocarcinoma and pancreatic cancer. A 5 unit increase in body mass index is associated with a 12 % to 51 % higher risk. Abdominal obesity is associated with esophageal adenocarcinoma and colorectal cancer beyond body mass index. Obesity has also been associated with a higher risk of liver and ovarian cancer, although supporting data is less abundant. The mechanisms underlying the positive association between obesity and risk of certain cancers have not been fully elucidated and differ by cancer site. Among the most important potential mechanisms are components of the metabolic syndrome, in particular insulin resistance and hyperinsulinemia, chronic inflammatory processes, sex steroid hormones as well as cytokines secreted by adipose tissue, including leptin and adiponectin
