To further explain this problem, we need to understand the pathogenesis of cancer first. When a cell has just become a cancer cell, it will have a "hidden shell" that looks like a normal cell, so the human immune system cannot quickly identify and kill these cancer cells. This is why it is difficult to diagnose many types of cancer in the early stage, because not all cancers have precancerous lesions, and the early symptoms of many cancers are not obvious, such as pancreatic cancer and liver cancer. Early symptoms are very subtle and difficult to diagnose. When the degree of cell canceration is gradually aggravated, immunity gradually loses its ability to kill cancer cells, which leads to cancer cells invading human organs and leading to malignant tumors. So many healthy people can't escape the "cunning killer" of cancer.
Secondly, people with good physical fitness usually have more confidence in their health. Under the influence of psychological function, I think I am in good health, and this disease is not easy to be found, so I ignore routine health care, such as physical examination. Even if you are sick sometimes, you will choose to "take a minor illness" and ignore the importance of medical care. In fact, health does not mean that the immune function of the body is completely normal, especially malignant diseases, such as cancer, whose causes are very complicated and have not yet been determined. People with strong immunity are less likely to get cancer. In other words, cancer is likely to attack people indiscriminately.
In short, the risk of cancer in human body can not be judged by physical quality alone. No matter whether the health condition is good or bad, everyone should eat healthily, exercise properly, advocate scientific physical examination, screen the risk of cancer, and make insurance for their own health!