Cancer and Exercise


This is not me, by the way. This is a stock photo to get your attention. I am  not this good looking.

Well, folks. I can’t run anymore. I can probably swim, though I haven’t tried. And after any significant cycling I am in a lot of pain, so I don’t  do that anymore.

But it was not always so. For sixty years I did martial arts, ran, played football and other sports, tennis, baseball, aerobics, step classes (yeah, that was neat, only guy among 40 females! Guys this is a great unsung secret. Try it. They’ll love you.), squash, water polo, basketball. I was awarded an Athletic Letter during my medical training, and in high school I was on the gymnastics team (where I lost a tournament to an amazing guy with only one leg). And I helped to start a karate school over twenty years ago.

So I have done my dues and although I am forced to coast now, I shall have to rely on those past endeavors. Now I can write.

Physical exercise can prevent cancer. There. I have said it. Most of you can close down your computer now and go and start walking, jogging, aerobics, martial arts, you name it.

A number of years ago I gave a talk to my medical colleagues on exercise and cancer. I researched it heavily, and concluded that it does work. I tell my patients about it, particularly my Breast Cancer patients. I really only treat Breast and Lung Cancer now, and a lot of my Lung Cancer patients are well past exercise, just like me. For me, it relates to musculo-skeletal issues; for them, it is their lung function. Smoking really messes them up.

The literature is persuasive, although the level of evidence is not robust. Having said that, I think there is enough, and more importantly I think there is a physiologic reason.

One thing about medicine. A lot is empirical, meaning ‘if it works, do it,’ but sometimes it is theoretical and logical, meaning, ‘hey, here’s why it works.’

For years we have known that exercise reduces the incidence of cancer. A cancer develops when a normal cell develops a mutation that turns it into a cancer. This is incidence. It is the beginning.

But we cancer doctors all know that many times cancers recur. Typically, remember, you can think of a cancer as a ‘Fuzzy Marble.’ Some of the fuzzy microscopic parts can get away before the surgery is performed, spreading unseen to other parts of the body; then a single cell doubles, and doubles again, and again, … it takes forty doublings to create a nodule big enough for anybody to find, and maybe twenty days between doublings. So that’s 40 x 20 is 800 days or about two and a half years for the single cell that got away to become a cancer metastasis that somebody can find.

This is recurrence of cancer, not incidence, and what amazed me when I first read about this was that exercise could help prevent this too.

Why? I wondered.

As Wolf Blitzer would say, ‘What’s going on?’

There are probably a lot of explanations, and those are important to researchers, people who are trying to figure out how to stop this process. But I am content for now with one good explanation. Something like my grandfather (who, in truth, I really didn’t like) would say, ‘a poor excuse is better than none.’

Well, a poor explanation is better than none.

Insulin is a growth hormone. It stimulates cellular growth. Oh, sure, you all know it reduces blood sugar, but that is a side effect. It helps to transport glucose (sugar) across cell membranes, which is required for cellular growth. And also required for muscle activity, by the way. So with better glucose transport, muscles work better. In fact, without glucose transport across muscle cell membranes, muscles don’t work at all.

Exercise increases glucose transport mechanisms across muscle cell membranes (by up-regulating glucose transport channels in muscle membranes). A lot. When this occurs, the need for insulin drops. When the need for insulin drops, insulin levels drop, and its tendency to stimulate cellular growth by increasing glucose transport also drops.

You all know that diabetic mothers give birth to big babies. (In general … not always … nothing in medicine is always). That’s because insulin is a growth hormone, with sugar (glucose)-reducing side effects.

So with less insulin, there is less stimulation of cellular growth, which includes cancer cells.

Less chance of cancer cells being stimulated to grow.

So it is that we have been looking at metformin, a drug used to control diabetes and sugar levels in the blood, as a method of reducing cancer recurrence by reducing the levels of insulin.

Thus, exercise reduces insulin, which reduces stimulation of cellular growth, which reduces cancer recurrence.

What level of exercise do you need?

It’s not  walk in the park, I’m sorry to say, though the walk in the park certainly can help.

Sitting quietly doing nothing for one hour is one Metabolic Equivalent Hour of energy expenditure. One MET!

If you walk briskly to the point of sweating, of being unable to talk in long sentences, of being short of breath, for one hour, you’re probably doing about 6-7 METs.

If you run hard for one hour–and not many of us can do that–you are probably in the realm of 10-12 METs in that hour.

If you can get 25 Met-Hours in a week, you are doing enough to reduce your cancer risk. Walk briskly to the point of sweating and being too short of breath to talk, 3 hours a week, or six half hours a week, you can reduce your risk of cancer. Maybe 10-20 percent. Maybe sometimes as much as chemotherapy can do, although the effects are additive to some extent … exercise is not a replacement for active treatment by your medical and/or radiation oncologist.


If you decide you don’t want to do, or cannot do, what your medical oncologist suggests, for many cancers (probably not all), exercise at least will give you some protection which YOU CAN CONTROL YOURSELF.

And it sure helps for lung, heart, vascular, mental health, muscle, endocrine … so much you can really do for yourself.

Mental health. Here, I don’t need clinical studies. I’m sure they exist. But every oncologist has to deal with their own mental health issues. Enough said? Just stop and think for a second. I have never met a patient who didn’t understand that part. They look at me sometimes and ask how I can do my job. Well, I love my job, but …

Oncologists have a rough time, and in this study of one person (me), well, exercise has been my savior!

So, stop reading this nonsense, and go out and walk!



3 thoughts on “Cancer and Exercise

  1. “For sixty years I did *marital* arts, ran, played football and other sports, tennis, baseball, aerobics, step classes (yeah, that was neat, only guy among 40 females!”

    I can’t help but notice the typo there! 😉

    On a serious note – I was surprised that running hard (10-12 METs) barely has twice the effect of a brisk walk (6-7 METs). Is the body more efficient when ‘pushed’, or is it that the stats from each activity come from different control groups (with different bodies)? Either way, you’re motivating me to get out for a lunchtime walk later!


    1. If I recall, obviously a lot of this is estimation from what is considered same level of exercise, but as with everything, it all depends on what you put into it. I think some researchers have made this determination using oxygen consumption as a measure of MET, and have been able therefore, with treadmill testing, to compare jogging with running hard. Many confounders of course, not the least of which is that the guy who can run hard for an hour may be able to do that more easily than I can jog for half an hour 🙂


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