1, it is well known: excess nutrition will cause obesity, thus inducing diabetes. Then what is obesity? In 2003, “Chinese adults overweight and obesity prevention and control guidelines” to BMI value ≥ 24kg/m2, for overweight, ≥ 28kg/m2 for obesity, male waist ≥ 85cm and female waist ≥ 80cm for abdominal obesity. BMI = weight (kg) / height (m) 2. 2, whether we can think that under-nutrition will not suffer from diabetes? Actually not. Certain diabetic patients are not caused by obesity, but related to insufficient nutrition, most of them are weak and thin. What is the specific mechanism? ① Chronic malnutrition, especially protein deficiency, can cause insulin-producing pancreatic islet cells to first become hypersecretory and then fail. The decrease in the number of islet cells is proportional to the duration of the nutritional deficiency. This is due to the fact that the lack of essential amino acids affects islet cell neogenesis and replication, which results in functional failure and induces diabetes. (2) The damage effect of certain pathogenic factors on islet cells is enhanced due to nutritional deficiency. The detoxification function of the liver is low in undernourished people, and the damage to islet cells by toxins from certain foods is increased, while vitamin deficiency decreases the function of islet cells. (3) Diabetes is closely related to heredity, viral infection and autoimmunity. Severe nutritional deficiency and protein deficiency make the body resistant, which increases the chance of viral infection and stimulates autoimmune pancreatitis, which destroys islet cells and leads to the development of diabetes. Patients with type I diabetes and diabetes secondary to hepatitis are clinically seen to be associated with these causes. Nutritional deficiencies can likewise contribute to the expression of genetic factors in some diabetic patients. Therefore, under-nutrition should be given as much attention as over-nutrition, so weight loss should not be excessive, or it will backfire.