Sex and Gender Perspective in Obesity and Gastric Cancer

There is sex difference of obesity and it might be related with sex hormones. For instance, estrogen regulates adipose tissue function and fat deposition by activation of the sympathetic nervous system, which leads to more adiposity in subcutaneous fat instead of visceral fat. There are strong evidences for the association between obesity and cancer, predominantly cancers of digestive organs including cardia gastric cancer (GC) and cancers of hormone sensitive organs in females. The main pathways linking obesity and cancer are hyperinsulinemia/insulin resistance and abnormalities of the insulin-like growth factor (IGF)-I system, sex hormone biosynthesis and pathway, and subclinical chronic low-grade inflammation and oxidative stress. There have been several reports regarding the effect of obesity on the development of cardia GC, especially in males. The body mass index (BMI) changes from underweight or normal to overweight (23.0–24.9 kg/m2) decrease the development of non-cardia GC in males but not in females. The prognosis of GC is the better as the BMI is higher, especially in males. Estrogen can explain for the sex difference of non-cardia cancer (mainly intestinal type) regarding obesity. The peripheral adipose tissue is responsible for the process of steroid aromatization to produce sex hormones including estrogen which can explain why the obese males have better survival or less development of non-cardia GC. In terms of cardia GC, the main cause is related with frequent gastroesophageal reflux in obese males. In addition, metabolic factors such as cholesterol, glucose and IGFs are related with GC similar to other obesity related cancers.