With the improvement of people’s living standard, lifestyle, diet structure and other changes, the ranks of obese people are growing day by day, obesity is not only related to cardiovascular and cerebrovascular diseases and diabetes, but also related to the occurrence of many kinds of cancer. The latest reports from the American Association for Cancer Research and the World Health Organization both agree that obesity has become a major cancer-causing factor in the world. There are many reasons why obesity increases the chance of developing cancer. Firstly, many carcinogenic substances and harmful substances are fatty and accumulate in fat, and the more animal fat is consumed, the greater the possibility of cancer. Secondly, obese patients often have high blood fat, which has an inhibitory effect on immune cells (such as macrophages), causing the body’s immune function to decline and the ability to identify and kill cancer cells to decrease. Thirdly, excessive body fat can cause “estrogen dominance”, thus inducing breast cancer and uterine cancer. At present, it is believed that the cancer closely related to obesity mainly includes breast cancer, endometrial cancer, kidney cancer, colon cancer and other four kinds of cancer. Breast cancer: The occurrence and development of breast cancer is related to estrogen, and the higher the level of estrogen, the more likely to suffer from breast cancer. In normal women, estrogen is mainly secreted by the ovaries. In addition to the part of estrogen secreted by the ovaries, fat cells can also produce estrogen in obese women. This is also a cause of breast cancer. After menopause, obesity becomes the main source of estrogen production in women. Therefore, women who are overly obese, especially those who become fat after menopause, have an increased chance of getting breast cancer. Therefore, reasonable diet and exercise is the best way to prevent breast cancer. 2.Endometrial cancer: As most obese people may have high blood pressure, high blood sugar and endocrine hormone disorder, among which estrogen is the main factor to induce endometrial cancer. Menopausal women who are obese have a higher chance of developing this kind of cancer. Therefore, obesity has been considered as a high risk factor for endometrial cancer. Once obese women have menstrual disorders, delayed menopause or abnormal vaginal bleeding after menopause, they should go to hospital for examination as early as possible. 3, kidney cancer: Swedish Karolinska Institute researchers found that morbidly obese people compared with normal weight people, the risk of kidney cancer is twice as high, overweight caused by the risk of kidney cell cancer for men and women are the same. Some studies believe that the level of certain hormones (such as insulin) in the body of obese people is elevated, which promotes the growth of renal cell cancer; and obesity can affect the blood supply of the kidneys, making the kidneys more sensitive to carcinogens. 4.Colorectal cancer: China’s statistics show that the prevalence of colorectal cancer has risen from one in 10,000 in the 1960s to six in 10,000 today, becoming the “oldest cancer” after stomach cancer and lung cancer, and there are about 130,000 new cases of colorectal cancer in China every year, and the trend is increasing year by year. In recent years, colorectal cancer, which mostly occurs in middle-aged and elderly people, has frequently attacked young people. In the high incidence area of colorectal cancer, young people less than 40 years old, colorectal cancer accounts for 2.2% to 4.5% of the total number of colorectal cancer. Surprisingly, the proportion of colorectal cancer among young people in China is 4 to 10 times higher than that in Europe and America. The main culprit of colorectal cancer is the frequent consumption of high-fat food. On the one hand, the more animal fats are consumed, the greater the risk of dissolving and absorbing carcinogenic substances. On the other hand, when digesting high-fat food, the gastrointestinal tract needs more bile, and the extra bile is decomposed by intestinal bacteria, which can produce carcinogenic “secondary bile acids”, and this carcinogen acts on intestinal mucosa all year round, which can easily make intestinal mucosa cancerous. A study conducted by the University of Tokyo in Japan shows that there is a direct relationship between the degree of obesity and the occurrence of colorectal cancer. The higher the degree of obesity, the greater the chance of getting cancer. Some obese patients who had suffered from colorectal cancer can also reduce the recurrence rate of cancer if they can lose weight successfully.