The role of food and nutrition in the prevention and treatment of cancer has always been the focus of cancer research, especially in the prevention of cancer.In 1981, the British oncology epidemiologists Doll and Peto, in their monograph “The Causes of Cancer”, were the first to suggest that “about 35% of deaths due to cancer in the United States are dietary related”. A large number of nutritional epidemiological studies have confirmed that the occurrence of a variety of tumors is related to dietary nutrition. For example, high-fat diet and obesity are related to breast cancer, pancreatic cancer and colon cancer, consumption of aflatoxin-contaminated food is related to liver cancer, and consumption of pickled food is related to gastric cancer and esophageal cancer. Patients with malignant tumors, especially those with crip tumors, in the treatment period and early recovery period, due to the tumor itself and the effect of anti-tumor therapy, often lead to poor appetite and reduced intake, causing weight loss, inducing or aggravating malnutrition. And in the treatment and rehabilitation period of malignant tumors, maintaining a stable body weight and keeping an ideal body weight is beneficial to the patients’ prognosis. A number of studies have demonstrated that patients who lose weight, or/and muscle mass, experience poor outcomes, including decreased quality of life, increased incidence of adverse effects of treatment, decreased treatment tolerance and compliance, shorter survival, longer hospitalization, and increased hospitalization costs. The primary, basic, and simplest way to maintain and keep an ideal body weight is through proper diet and exercise. Food choices should be diversified and it is not recommended to exaggerate the anti-cancer effects of certain foods to prevent unbalanced nutritional intake. It is recommended to increase the protein content in the diet and consume more high-quality proteins to alleviate the decrease in protein degradation and protein synthesis caused by tumors. To combat tumors, it is recommended that you consume adequate amounts of vegetables, fruits, and other plant foods to ensure adequate intake of vitamins and minerals. Since tumor cells have a high capacity for glucose uptake and metabolism by glycolysis, it is recommended to limit the intake of sugar, especially refined sugar.