Many patients ask me whether obesity is a direct cancer-causing factor. In fact, the exact mechanism that induces the occurrence of cancer is not known. However, it is not difficult to understand the relevance of this when you look at the lifestyle habits of fat people. Obese patients tend to prefer foods high in calories, animal fat, trans fatty acids and refined carbohydrates, while the intake of dietary fiber, whole grain carbohydrates, vegetables and fruits is insufficient. Such a diet will make the body’s hormone imbalance. This is because the adipose tissue in obese patients will secrete too much aromatase, speeding up the conversion of estrogen precursors to estradiol and raising serum estradiol levels. High estrogen levels are associated with the development of many types of cancer, such as breast and endometrial cancers. Also, overweight and obesity will directly lead to insulin resistance, thus causing hyperinsulinemia, which affects the regulatory cycle of cell growth and accelerates genetic mutations and the development of cancer. The most appropriate BMI (body mass index) is 22kg/m2 [BMI = weight (kg) ÷ height (m) squared], below 18kg/m2 is also detrimental to health and can increase the risk of cancer, such as lung cancer. Stomach reduction surgery to prevent tumors It is now clearly known that fat is one of the causes of tumors, and to prevent the occurrence of tumors, the most basic root problem – obesity – should be solved. When the body mass index increases every 5(kg/m²) from the normal basis, the probability of tumor occurrence increases, while when the weight drops to the normal BMI level, then the probability of tumor occurrence is greatly reduced. As for people with high BMI, having gastric reduction surgery is the only effective way to obtain long-term effective weight loss and to prevent related complications, such as tumors. In the long term, after the implementation of gastric reduction surgery, patients can generally lose 50% to 60% of their body weight, and a 14-year long term study also showed that the effect brought by gastric reduction surgery is sustainable, so tumors need not be afraid, a healthy weight is a good way to prevent tumors.