fitness · research

Is high-intensity exercise the new cancer drug? Way too soon to tell

Last week, a new study came out on the effects of high-intensity exercise on metastatic (late stage) cancer. Medical news sites and medical Twitter have been all abuzz about the results. Take a look:

From Medical News Today: metastatic cancer risk reduced by as much as 72% with high intensity exercise.

For those of you who know me or have read some of my critiques of medical journalism, you might think I’m about to lower the boom on the journalists and twitterers who are very enthusiastic about the results of the study. I’m not doing that. Not today… But, a little unpacking and clarifying of what we now know (and don’t know) about exercise and cancer is in order.

Please, take a seat. But I promise not to be long.

First of all, what were the researchers looking for in this multi-part study?

Researchers hypothesize that exercise-induced metabolic reprogramming of organs transforms them into metastatic-resistant metabolic micro-environments by limiting nutrient availability to the cancer cells thus creating a metabolic shield.

That is, they were investigating whether the metabolic effects of exercise might increase the likelihood that our organs would consume more glucose than usual, depriving tumors of the nutrients they need to grow and migrate.

Spoiler alert: the results of their study suggest a “yes” answer.

Exercise protects against cancer progression and metastasis by inducing a high nutrient demand in internal organs, indicating that reducing nutrient availability to tumor cells represents a potential strategy to prevent metastasis.

But (and as RuPaul says, it’s a big but), the details of the study show the results to be promising but still preliminary.

from the study:

Epidemiologic data from a 20-year prospective study of a large human cohort of initially cancer-free participants revealed that exercise prior to cancer initiation had a modest impact on cancer incidence in low metastatic stages but significantly reduced the likelihood of highly metastatic cancer.

In a 20-year prospective study of 2734 men and women in Israel, researchers found that high-intensity exercise lowered the relative risk for more advanced/metastatic stages of cancer (e.g. spreading to other sites in the body) 72%, compared to low-moderate exercise. Note, this is relative risk, not absolute risk. And, this is population-level, not taking into account other factors that strongly influence individual baseline risk. One more and: the researchers say that much more research is needed to know more about which particular cancers respond to increased exercise. All of this is TBD, if incredibly promising.

The study also included an analysis of this effect in mice.

In three models of melanoma in mice, exercise prior to cancer injection significantly protected against metastases in distant organs. 

Note, this experiment was done with melanoma, one form of cancer. It’s well known that different cancers set up shop, as it were, in the body in very different ways. Again, the effects of increased exercise on other cancers is still TBD.

There were other analyses done, and if you’re up to the task, you can access the whole paper here.

The authors themselves issues a bunch of caveats at the end of the article. For instance, the literature doesn’t show how long the tumor-starving effects of intense exercise last. They also point out that high-intensity exercisers, like Olympic athletes, are not themselves immune to various cancers. This suggests to them that “a personalized exercise regime for each patient might provide better clinical outcomes.”

Yes, I fully concur. Until we know more– a lot more– we can conclude that all forms and intensities of exercise are, in many ways, good for health ad longevity. A Healthline article on this study agrees:

High intensity also might not be possible depending on age and other factors. For these people, even moderate exercise still has a protective effect against cancer, Hicks said.

“Hundreds of epidemiological studies, comprised of millions of participants, provide strong evidence that regular, daily activities like brisk walking significantly reduce the risks of many cancers,” he said. “These results show 10 to 20 percent risk reductions for bladder, breast, colon, endometrial, esophageal adenocarcinoma, and renal and gastric cancers.

Well, yay for that! Reading those words has given me enough energy to maybe do this high-intensity move:

A woman in jeans and a sweatshirt, Jumping for joy! By Hannah Busing, for Unsplash.
Jumping for joy! By Hannah Busing, for Unsplash.

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