The data in this study is more interesting for the size of the effect than for the reduction in metastatic cancer risk in and of itself, as one expects exercise to reduce manifestations of aging across the board, via many direct and indirect mechanisms. Whether the important mechanism in this case, as the researchers suggest, that high intensity exercise consumes metabolic resources that would otherwise be available to tumor tissue, is an open question. It could well be effects on immune surveillance, for example, or any number of other differences in metabolism, such as reduced levels of chronic inflammation, that act to make a less hospitable environment for metastasis.
Studies have demonstrated that physical exercise reduces the risk for some types of cancer by up to 35%. This positive effect is similar to the impact of exercise on other conditions, such as heart disease and diabetes. In this study researchers added new insight, showing that high-intensity aerobic exercise, which derives its energy from sugar, can reduce the risk of metastatic cancer by as much as 72%. If so far the general message to the public has been ‘be active, be healthy’, now researchers can explain how aerobic activity can maximize the prevention of the most aggressive and metastatic types of cancer.
The study combined an animal model in which mice were trained under a strict exercise regimen, with data from healthy human volunteers examined before and after running. The human data, obtained from an epidemiological study that monitored 3,000 individuals for about 20 years, indicated 72% less metastatic cancer in participants who reported regular aerobic activity at high intensity, compared to those who did not engage in physical exercise.
The animal model exhibited a similar outcome, also enabling the researchers to identify its underlying mechanism. Sampling the internal organs of the physically fit animals, before and after physical exercise, and also following the injection of cancer, they found that aerobic activity significantly reduced the development of metastatic tumors in the lymph nodes, lungs, and liver. The researchers hypothesized that in both humans and model animals, this favorable outcome is related to the enhanced rate of glucose consumption induced by exercise.