In April, the AARP asked me to help moderate an international meeting of 15 exercise scientists in Vancouver. Their goal was to write a consensus statement about how best to use exercise to promote health (specifically “brain health”). What types of exercise are ideal? Is walking as good as running? Does yoga count? How do we measure exercise—as a matter of heart rate, calories burned, or simply of time spent? All or none, of these?
I was blunt about my skepticism. These are huge questions. I’m not convinced that brain health is a thing that can be pursued separately from any other type of health. And I’ve been in enough meetings where scientists try to reach a consensus. It’s fun if you’re into watching people argue.
Which I am, so I said I’d do it. It seemed like a learning opportunity, and I like threatening to cut people’s microphones when they talk too much (even when I don’t actually have that power). So I flew to Vancouver, to a windowless conference room. All of the scientists sat the entire time, as people in meetings do, even when they’re exercise scientists. I paced in the back as the debates drew on.
But despite my pessimism and negativity, they ultimately accomplished more than I expected. The AARP published its statement last month. First among the experts’ conclusions was, somewhat on the nose, “physical activity has a positive impact on brain health.” Even that was a contestable assertion. But, the group concluded, “Based on epidemiological evidence, people who lead a physically active lifestyle have lower risk of cognitive decline.”
Unlike testing the effectiveness of a pharmaceutical, testing the effectiveness of a complex intervention like decades of a physically active lifestyle is not well suited to randomized, controlled trials. So epidemiology—showing a correlation like this—is usually the best evidence we have.
As for what counts as physical activity or exercise, and how much and what types are beneficial for any given person, though, the discussion came recursively back to that same old refrain: consult your doctor or health professional. Maybe you have a bad knee, so I can’t even recommend walking. Or a bad back, and yoga is precarious.
But even if one’s doctor is trained in prescribing exercise, telling everyone to talk to their doctor makes for a tepid and expensive public-health movement. Is there nothing that can be said as a blanket recommendation for everyone—a pithy phrase that people can keep in mind as a basic principle? Something like what Michael Pollan did for dietary recommendations with “Eat food. Not too much. Mostly plants.”
A vague understanding that more exercise is better doesn’t work, because more is not always better, and routine exercise is not clearly superior to an overall active lifestyle. There are diminishing marginal returns with working out, as with salads, and in all things.
But as a matter of motivational psychology, it’s beneficial for most people to have concrete, attainable goals. Largely for that reason, the CDC recommends 150 minutes of “moderate-intensity aerobic activity” every week, in addition to “muscle strengthening activities” on two or more days. 150 minutes is not because 160 minutes wouldn’t be better. Or because 150 minutes is substantively much better than 140. The recommendation is based on what will actually get people to move. 150 minutes offers a mix of structure and flexibility. Saying 20 minutes a day is too prescriptive—people miss a few days and then give up on the whole thing. Saying 600 minutes a month is too vast and remote. So it’s 150 minutes per week.
But these well-considered recommendations may be missing a critical element in effectively using physical activity to promote health.
The American Heart Association recently held a consensus meeting similar to the AARP’s. But their statement, published today in the journal Circulation, takes the discussion in a different direction. Fourteen cardiovascular-health experts from around the country convened and reviewed all the relevant research about the health effects of physical activity. While the panel did support the 150-minute recommendation, it made a more important point: An independent problem, in terms of cardiovascular health and diabetes, isn’t the time we spend exercising, but the time we spend not moving at all.
The main conclusion is that vigorous physical activity (the more explicit, clinical term for “exercise”) doesn’t cancel out the negative impact of time spent being sedentary, which appears to increase the risk of cardiovascular disease (the leading cause of death) and diabetes, even among people who exercise regularly.
In a press statement, the chair of the group, Deborah Rohm Young, the director of behavioral research at Kaiser Permanente Southern California, put it this way: “Regardless of how much physical activity someone gets, prolonged sedentary time could negatively impact the health of your heart and blood vessels.”
Or, as I’m putting it, you can’t undo sitting. Which sounds preachy—so, it’s fine if you want to sit, I mean, that’s up to you. It should just be an informed decision. This is why I’m bad at writing these health aphorisms.
But I’m as guilty as anyone of thinking I can sit in a conference for 10 hours and then go run a few miles and it all balances out (which I did in Vancouver). That sort of bargaining is commonplace in health: Last month in The Lancet, researchers tested whether any amount of exercise could ameliorate the risk of premature death that comes with sitting for eight hours a day. Their epidemiological analysis found that 60 to 75 minutes of concerted daily exercise might do the trick. Which is a lot. And the people weren’t necessarily healthy, just alive.
The aggregate message at this point seem to be to run if you like running—and for the psychological and assorted metabolic benefits—but not as a means of justifying an otherwise sedentary life. Just like a salad doesn’t undo a cigarette, and a donation to Goodwill doesn’t undo replacing a friend’s sunscreen with shampoo.
This seductive trade-off psychology may also explain why the American Heart Association’s review concluded that: “Interventions focusing solely on reducing sedentary behavior appear to be more effective at reducing sedentary behavior than those that include strategies for both increasing physical activity and reducing sedentary behaviors.” According to that, maybe we are devoting too much to advocating exercise and not enough to simply demonizing sedentariness. Maybe we should—at least in some cases—drop advocating “exercise” altogether?
The American Heart Association doesn’t go that far this week, but its ultimate conclusion is subtly radical: “absence of sufficient data to recommend qualitative guidelines, it is appropriate to promote the advisory, ‘Sit less, move more.’”
And by “move,” they mean almost anything that is not sitting or reclining—anything that increases your metabolism to 1.5 times that of being absolutely still. Which is a very low bar. “Leisurely walking” is close to 2.5, while gardening or throwing a baseball with a kid gets you closer to four.
That is what you get once you distill all the evidence for all the people. Sit less, move more. It’s as scientific as the best experts can give us, and simple enough to stick with people. Exercise might have a Pollan-esque mantra here that could endure.
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