The authors make it quite clear that they are not talking here about merely accumulating the equivalent of an hour of exercise during one's routine daily activities (such as climbing stairs or doing the laundry). No, they're talking about adding 60 minutes of honest to goodness exercise (the equivalent of walking or jogging at least at a 4 to 5 miles per hour pace) to whatever other activities we might perform during the course of a normal day.
How did they come up with an hour a day?
The panel of authors who wrote this report for the IOM are scientists. Every word in this report is backed up by references from the latest scientific studies, carefully interpreted in light of the whole body of scientific evidence. This report is a comprehensive synthesis of what is known and unknown today about optimizing our caloric intake (carbohydrates, fat, protein, etc.) and our output (physical activity) in order to maintain an advisable weight, a favorable body composition (i.e., proportion of muscle to fat), and cardiovascular health. And based on their synthesis of all this data, the authors' conclusions regarding exercise are quite straightforward and objective. To maintain optimal cardiovascular health, a good body weight, and a favorable body composition, we really ought to be exercising at least an hour a day. If you don't believe it, study the report and do the math yourself.So what's the problem?
While an hour a day of exercise might be just the thing for us, it is entirely ridiculous to expect us all to change our fundamental natures just because a top scientific panel, following high-quality investigational methodologies, blandly suggests we should. To be useful, expert recommendations on a healthy lifestyle must remain within the bounds of the possible. And telling us to exercise an hour a day is more than just out of bounds - it is too outlandish for words. Indeed, this new recommendation is so outlandish that it threatens to completely undermine whatever good might have come so far from past, and more reasonable, recommendations on exercise.DrRich's fear is that typical, normal Americans, upon learning that all their efforts to fit at least some exercise into their busy schedules are, after all, laughably inadequate, are going to throw up their hands in sheer frustration and disgust and say, "Screw it, Tillie. Pass the remote and open a bag of Cheetos." DrRich suspects this is true because, well, that was very nearly his reaction to this new report.
How much exercise is really necessary?
Here's a fact: the more exercise you do, the more you are reducing your cardiovascular risk. While the IOM is now on record as saying we "need" to do an hour a day of exercise, the fact is that if we did two hours a day we'd be even better off. (To this extent, the scientist-authors of this report maintained at least some sense of practicality.) Those of you who can fit in an hour or two of exercise a day need read no further. But for the rest of us, the real question is: How much exercise do we really need in order to see at least some substantial cardiovascular benefit?More than 40 studies in the scientific literature document that cardiac risk can be reduced by 30 - 50% by regular, moderate exercise - exercise averaging far less than one hour per day. Indeed, on September 5, the very day the Institute of Medicine report was released, yet another major article appeared in the New England Journal of Medicine showing that, among 73,743 women followed for a number of years, those who reported walking at least 2.5 hours a week (roughly 20 minutes a day) reduced their cardiovascular risk by 30%. Women who exercised more than this reduced their risk even more, but the point is that 20 minutes a day was enough to gain a substantial improvement in cardiac risk. This study is consistent with a large body of medical literature.
The bottom line: if you can engage in vigorous exercise for an hour a day without making yourself crazy, crippling yourself, losing your job, or instigating a divorce, then by all means do so. But if you are a mere mortal, then at least try to go for a walk every day. Twenty minutes of moderate daily activity won't make the pounds melt off or give you the same body composition as Frank Shorter or the Williams sisters, but it will make a real impact on your cardiovascular health. If the IOM report had allowed as much, frustration levels among those of us trying to lead healthy, but non-obsessive, lifestyles would be a little bit lower today.
