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.
Really?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.
My 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." I suspect this is true because, well, that was very nearly my reaction to this report.
How Much Exercise Is Really Necessary?Here's a fact: the more exercise you do, the more you are reducing your cardiovascular risk, and the more calories you burn off. 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?
The answer is: 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. If you can exercise at a moderate pace for 20 - 30 minutes at least five days a week, you may not shed pounds, but you will be doing your heart and your cardiovascular system a lot of good.
The bottom line: if you can engage in vigorous exercise for an hour a day without making yourself crazy, disabling yourself with orthopedic issues, 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 Lance Armstrong or the Williams sisters, but it will make a real impact on your cardiovascular health.
If the authors of the IOM report had allowed as much, the frustration levels they created among those of us trying to lead healthy, but non-obsessive, lifestyles would be a little bit lower.
Panel on Macronutrients, Panel on the Definition of Dietary Fiber, Subcommittee on Upper Reference Levels of Nutrients, Subcommittee on Interpretation and Uses of Dietary Reference Intakes, and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes For Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Institute of Medicine; The National Academies Press, Washington, DC, 2005.
Pate RR, Pratt M, Blair SN, et al. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 1995 Feb 1;273(5):402-7.
Fletcher, GF. How to implement physical activity in primary and secondary prevention. A Statement for Healthcare Professionals from the Task Force on Risk Reduction, American Heart Association. Circulation 1997; 96:355.