Jerusalem Post

ByWALLA! HEALTH

Numerous studies have found the benefits of physical activity for every organ and part of the body. A new study suggests that the fitness you do does not allow cancer to grow.

A long line of studies has already shown that physical activity reduces the risk of cancer, but until now it was not clear what exactly underlies this connection. A new study in mice, conducted at Yale University, offers a simple and fascinating explanation: During physical activity, the muscles “draw” more energy, thereby preventing the tumor from receiving the fuel it needs in order to grow.
The researchers followed mice that carried breast cancer tumors or skin cancer, and divided them into groups according to diet and level of activity. Using molecular markers, they tracked the path glucose takes in the body, and discovered that the animals that engaged in physical activity diverted a large portion of the energy to the muscles – at the expense of the cancer cells.
The result was very clear. After four weeks of continuous physical activity, obese mice that trained regularly developed tumors that were about 60 percent smaller compared to obese mice that did not train. The researchers also found hundreds of genes related to metabolism that operated differently in the active mice, indicating that the cancer cells entered a survival state of high stress.

One of the interesting findings was a decrease in the activity of a protein called mTOR within the tumors – a protein that encourages cell growth. A decrease in its activity may be an important clue for the development of new treatments.

The researchers emphasize that glucose is probably a central player in the effect of physical activity on slowing tumor growth. In simple terms, the body channels sugar to the muscles, leaving less of it available to the cancer cells.
Of course, cancer is a very complex disease and it cannot be prevented solely through brisk walking or strength training. But the study shows that physical activity may be a significant component in reducing the risk of tumor formation. Even activity performed two weeks before the implantation of the tumor caused the tumors to be smaller.

The researchers note that the fact that this mechanism appeared both in breast cancer and in melanoma suggests that the effect may be broader and not limited to just one type of cancer.
Is this also true in humans? It is still not clear. The next step for the researchers is to examine human tumors and check how different types of activity affect them. A better understanding of these mechanisms may pave the way for new treatments, especially for people who are unable to perform physical activity.