I have lately found myself bombarded with pressure to exercise. Part of it is New Year’s resolutions, to be sure, but even the scientific literature has joined the lobbying effort. In October, the British Medical Journal published a review article suggesting that exercise and drug treatment were similarly effective at preventing heart disease mortality. Coverage of this study touted the benefits of exercise, with headlines like “Exercise ‘as good as medicines’ in treating heart disease.” Even Slate got on the bandwagon, arguing that exercise is a “free and readily available” way to treat many diseases.
The policy argument, either explicit or implicit in these pieces, is that doctors should spend more time encouraging their patients to exercise. Or they should consider prescribing exercise rather than drugs to treat some conditions. Or that we as a society should pay people to exercise. Really, anything to get people to exercise more because, it seems, exercise is a cheaper way to deliver the same health benefits you’d get from drug treatment.
As an occasional exerciser, I appreciate the opportunity to feel more virtuous when I get around to working out. But as an economist, I can’t help but feel like this is a little backward.
The first thing to say is that exercise isn’t actually free. Even if you ignore the gym membership and forgo cute yoga pants, exercise takes time. And because your time has value (or, in a technical term, there is an “opportunity cost”) it is expensive to exercise even if all you do is put on your ratty old gym clothes and run around the block.
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But there’s another factor, which I think is probably a lot more important to consider: People hate to exercise. Not all people, of course, but a lot of them. And ignoring this is going to lead us to overvalue exercise. The way an economist would think about exercise includes both benefits and costs.
Think back to that study showing exercise and drugs are equally effective at preventing mortality. What we learn is that the benefits to the two things are the same – preventing mortality. As for the cost: For most people, taking a pill every day is preferable to having to adopt a rigorous exercise program. In truth, the coverage of this study should have been more like, “Exercise is no better for you than taking a pill and sitting on your butt in front of the TV.”
Interestingly, this also tells us something about why drugs that treat conditions related to obesity – statins for cholesterol, for example – are so valuable. People hate dieting just the way they hate exercise. Much of the benefit of these drugs are that they let you be healthy while engaging in all kinds of unhealthy behaviors. When they one day develop a gut bacteria treatment for obesity the big winners will not just be people who are obese now, but also those of us who would like to eat more junk food but try to restrain ourselves.
So, what do we conclude on exercise? Should doctors spend more time motivating their patients to exercise, rather than just prescribing them drugs? If we think exercise is free and easy, then of course they should. But once we recognize that it has a cost – monetary, yes, but also in enjoyment terms – this is much less clear. Let’s stop putting moral judgments on exercise, or the lack thereof. And let’s get to work on that gut bacteria treatment. Hurry up.
Emily Oster is an associate professor of economics at the University of Chicago Booth School.