Like everyone else who was ever diagnosed with type 2 diabetes, I was strongly advised to start an exercise program, and like everyone else I assumed that it probably wouldn't make a very big difference whether I did the exercise or not. In fairness to myself, I would like to point out that I had a perfectly sensible reason for making that assumption: I didn't want to do the exercise.

Because I didn't like exercise, I wanted to believe that exercise was not crucial, and on that basis I became skeptical of the claims that were made for it. Oh, I admitted that exercise might help. A little. I would try it for a while, just to be a good sport about the whole thing. But I certainly didn't expect much from it. At best, exercise would produce subtle, hard-to-measure benefits. Exercise was not medicine, after all. At least, it was not strong medicine. It could never do as much for me as the real thing.

I knew what real medicine was. It was, first and foremost, expensive. It was also hard to obtain -- you couldn't have it without your doctors permission. It came in the form of capsules or oddly-shaped little pills, nestled in an amber-colored plastic cylinder with a hard-to-remove white cap. It was accompanied by a much-folded leaflet explaining, in extremely small print, that you shouldnt be entirely surprised if these pills caused you to experience headache, throat irritation, blurred vision, nasal bleeding, weakness, trembling, vertigo, shortness of breath, dry cough, muscle sorenesss, nausea, abdominal cramps, thirst, rash, insomnia, night sweats, discoloration of tooth enamel, and numbness in the fingers and toes. It might also cause you to suffer from vaginal dryness and erectile dysfunction, though presumably not at the same time. Oh, and your future children might be lizards.

Now that was what I called real medicine! The high price, the legal restrictions, and the threatened side-effects did not really seem like disadvantages; they seemed like proof that this was powerful stuff that really worked.

And so, when I saw people waiting in line at the pharmacy, I thought they were receiving medical treatment. When I saw amateur athletes, clad in brightly colored exercise clothing, running around Spring Lake or pedaling their bicycles over Chalk Hill, I thought they were mostly making a fashion statement. Any benefit that these people were deriving from their healthier-than-thou public displays was incidental (and probably small).

However, despite that reluctance to accept the obvious which I share with so many of my fellow citizens, I decided to read up on the matter, and see how exercise stacked up against pharmaceuticals in terms of effectiveness. I soon found out that, sure enough, exercise is not medicine. It is better than medicine and by a surprisingly wide margin.

When I say that exercise is not medicine, and also that exercise is better than medicine, I am equally serious on both points. As these points require some explanation, I will do my best to provide it.

In recent years, exercise has increasingly come to be seen as a kind of therapy. It is a recommended treatment for many different health problems. Some doctors go so far as to say that, if exercise could be delivered in the form of a pill, they would find themselves writing more prescriptions for that than for anything else, because exercise is effective against so many different disorders.

Of course, nobody really believes (even in this era of biotechnology, nanotechnology, and genetic tinkering) that the health benefits of exercise ever will be delivered in the form of a pill. Exercise is a behavior rather than a drug; this makes it strikingly different from other medical treatments. Exercise requires (and in fact consists of) the patients active participation. Other medical treatments require so little from the patient that most such treatments can be administered to a patient in a coma. Exercise is simply not like other kinds of medicine.

Nevertheless, the exercise-as-medicine concept does seem like a handy metaphor. After all, there are many millions of Americans who have health problems for which exercise is a useful remedy:
  • Too much body fat? Exercise burns it.
  • Too much LDL cholesterol? Exercise reduces it.
  • Too little HDL cholesterol? Exercise increases it.
  • Weak cardiovascular system? Exercise expands existing blood vessels, adds new ones, and boosts the hearts pumping capacity.
  • High blood pressure? Exercise reduces it.
  • Resting heart rate too high? Exercise reduces it.
  • Low stamina? Exercise increases it.
  • Weak, easily-fractured bones? Exercise strengthens them.
  • Weak, easily-strained muscles? Exercise strengthens them.
  • Blood sugar too high? Exercise reduces it.
  • Insulin-sensitivity too low? Exercise increases it.
  • Low muscle-mass? Exercise promotes growth and renewal of muscle fibers.
  • Weak immune system? Exercise strengthens it (thus reducing the risk of infectious disease, and maybe even cancer).
  • Too much stress? Exercise relieves it.
  • Low self-confidence? Exercise builds it up.
  • Moody or depressed? Exercise generally acts as a mood-stabilizer, and relieves or prevents depression.
Looking back over that list, and considering it as a whole, what do you notice about it? Unless youre a more trusting soul than I am, the main thing you notice is that it sounds too good to be true. Outright impossible, in fact.

How could one remedy be effective against all those seemingly unrelated problems? What do muscle fibers have to do with depression, and what does blood sugar have to do with bone density? There seems to be no logical reason why one treatment would have a beneficial effect on such a long list of problems. If I were talking about a new drug here, or some herbal supplement called Moon Wortle or Dragon Grass, I hope your reaction would be one of extreme skepticisim. So lengthy a list of benefits can only remind us of the absurd claims made for various 19th-century patent medicines, each of which was supposedly effective against consumption, catarrh, scarlet fever, drospy, nervous hysteria, loss of conjugal ardor, and every other malady that people of that era worried about, including old age itself.

I am not trying to suggest that the claimed health benefits of exercise arent real; the evidence says pretty firmly that they are. Strange as it seems, exercise really can do all the things for you that I have described and that alone is enough to make exercise seem decidedly unlike medicine. There is no drug that can do even half of the things that exercise can do for you. And medicines have undesirable side-effects; exercise has desirable side-effects.

One could argue that these differences merely prove that exercise is the best of all medicines. I would argue that they prove something else: that exercise is fundamentally different from all medicines, and that when we define exercise as a kind of medicine we are somehow missing the point.

I say we need to re-think this. What matters about exercise is not that it is therapeutic in many situations, but that doing without it is destructive in all situations. To put it another way, life without exercise is a disease condition. We need to stop thinking of exercise as a therapy, and start thinking of it as one of the necessities of life.

The realization that physical activity is necessary to health has been slow in dawning. Not so very long ago, it was assumed that inactivity was therapeutic. Patients recovering from surgery or a severe illness were urged to get plenty of bedrest, and nothing but bedrest, if they wanted to make a full recovery. Clinical experience eventually made doctors wonder why, if bedrest was such a great boon to the healing process, the patients who stayed in bed day and night were taking so long to recover, and were developing so many additional health problems along the way. Sure enough, studies of healthy young volunteers showed that prolonged bedrest was enough, all by itself, to cause a serious decline in the health of anyone who got too much of it.

To be sure, a certain amount of rest is necessary, but more is not better. For whatever reason, the human body is designed to be active, and things start to go very seriously wrong with it if it is inactive for too long. (That is why, these days, post-operative patients are asked to get up and walk around so soon after surgery.)

The human body has certain fundamental requirements (such as food, water, air, and sleep) without which it cannot maintain itself in a healthy condition. If any one of these requirements is not being met, various tissues, organs, and systems throughout the body begins to malfunction, and health in general deteriorates resulting in a cascade of seemingly unrelated medical problems. How long it takes for these harmful consequences to occur depends on which requirement isnt being met. (Running out of air is a more immediate crisis than running out of food.) But whether we start to pay the price minutes from now, hours from now, or months from now, attempting to do without one of the bodys fundamental requirements is broadly and inescapably harmful to human health. Even sleep deprivation, which most of us assume will make us feel bad without actually injuring us, can in fact do quite serious physical harm (one study of the effects of sleeplessness on healthy volunteers had to be stopped because several of the test subjects were becoming diabetic).

It turns out that exercise is one of those fundamental requirements of the body, and that doing without it over a long enough period causes a bewildering variety of health problems to occur. When we say that exercise is effective against an amazing number of diseases, weve really got it backwards. The truth is that all those diseases are consequences of the kind of generalized breakdown that occurs when the bodys need for exercise is not being met.

Living without exercise has a widely destructive impact on the human body, just as living without food does. That is why, in a society which does not grasp that exercise is a basic requirement, exercise can appear to be broadly therapeutic. To say that exercise is a good remedy for cardiovascular problems, for example, isnt exactly wrong, but it seems a little dopey to put it that way, given that most common cardiovascular problems are the normal and expected consequences of physical inactivity. You might as well announce, in a tone of triumphant discovery, that one of the best therapies for the health problems associated with starvation is eating food. Its not exactly a dazzling insight, is it?

It isnt hard to understand why we need air, water, and food. On the other hand, its impossible to understand why we need sleep (most of us would be hard pressed to say what sleep is, much less explain why we need it). The need for exercise is somewhere in between these extremes. It isnt easily explained, but it at least it isnt as mysterious as the need for sleep.

Apparently the body needs exercise because the body is designed (1) to adapt itself to the physical conditions under which it is operating, and (2) to manage its resources carefully, wasting nothing. Nature assumes that different individuals will face different physical demands, depending on where and how they live. Nature also assumes (with good reason) that food will often be in short supply. The best way for the body to ensure survival is to find a way to address both these issues at once, applying its scarce resources where they are most needed, and refusing to apply them where they dont seem to be needed at all. That is why muscles that are heavily used get bigger, and unused muscles tend to waste away. There is no good reason, after all, for your body to invest its scarce resources in maintaining muscle fibers that you arent using. It might as well break down those unused muscle fibers for the chemical energy that is in them chemical energy which might come in handy later if your food supply runs out.

This use-it-or-lose it principle applies to many processes in the body, not just muscle growth. The body maintains its various organs, tissues, and systems on the basis of need and need is defined in terms of usage. These maintenance processes respond to the stimulus given by physical exertion. Because the amount of response depends upon the amount of stimulation, the body is able to adapt itself to circumstances (that is, it responds most where the need is greatest).

There is nothing wrong with this approach, so long as humans live in a state of nature, and people have no choice but to lead a physically active life. In a state of civilization, with much of the need for vigorous activity eliminated, the bodys use-it-or-lose it priorities can work against our long-term health prospects.

Even those of us who make room in our lives for a daily workout are often sedentary the rest of the time. It's difficult to work out hard enough in 30 minutes (or whatever exercise time we've allowed ourselves) to make up for the fact that we're sitting in front of a computer several hours a day, and not out hunting bison. People who don't "work out" but whose daily routine keeps them engaged in physical work may actually do better than those who go to the gym every day. Even if you do exercise, it is also a good idea to move around a bit during the rest of your day. It helps if you recognize the lazy choices we are continually being tempted to make taking the elevator instead of the stairs, or circling the parking lot looking for a space that's as close as possible to the store, so that we don't have to walk a yard farther than necessary. The habit of immobility is a hard one to fight, even for athletes who happen not to be working out at the moment, but we all need to work on it.