Fat land : how Americans became the fattest people in the world (13 page)

When it comes to exercise, however, human beings are, in general, not a very "Wow! I can do that!" bunch. They are, after all, genetically programmed to conserve energy, to find every opportunity they can to ... sit on their duffs. Moreover, the new recommendations came at a time of unparalleled opportunity both to be sedentary and to consume huge amounts of fatty calories on the cheap. In the early 1990s supersize had met Super Mario with a vengeance; the price of both had dropped so much as to induce price wars.

WHY THE CALORIES STAYED ON OUR BODIES

Considering such a context, two questions seem appropriate. One, was telling people they could get by with less exercise a good idea? And two, was it true, or at least were the assumptions behind the advice true? On both counts, the evidence suggests an answer of no.

One way to gauge the response of the average American to the new guidelines is to look at the way they were presented by the media. True, the media (thank God) do not exactly represent the way the average Jane thinks, but the modern media are nothing if not absolutely addicted to the latest health manifestos. If skepticism about them is not their lot, the media's acceptance is largely based on ignorance and wishful thinking; to paraphrase Mr. Dooley, the newspaper bosses — they like to sit around and eat a Big Mac too.

Consider what they wrote in the aftermath of the 1993 guidelines: "Still don't exercise? No sweat. A little at a time now called enough" (Chicago Tribune); "Gym workout? U.S. says walking, gardening will do, too" (Boston Globe); "Study says you don't have to sweat fitness routine" (Los Angeles Times); "If you can't run for health, a walk will do, experts say" (New York Times); and "A walk is as good as a workout" (Atlanta Constitution). TV, as usual, trumped print. In one famous piece by a Los Angeles network affiliate, viewers were told that "even seriously hunting for the channel changer can count toward your daily thirty!"

No one can say exactly how the average American interpreted such drivel, but what, given the permissiveness of the overall culture, would be the better bet: that they would use it as an excuse, as a way to get off the hook, or that they would say, "Wow! I can do that"? The point is that no one on the reform committee seems to have understood the way American culture digests any form of reduced expectations. In this case, the media had transformed what was once a mere prescription to reduce a lazy man's chance of getting a heart attack into a national prescription for fitness. In the wishful-thinking, reality-denying, boundary-hating world of

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modern America, this was manna from heaven — a Whopper with cheese from the CDC!

For all of which the reformers can be forgiven. No one, after all, can ever truly gauge what the popular media will do with any given piece of scientific information. Yet science does answer to its own. And in that respect the reformers have much to reconsider.

How wise was it to base a recommendation for all Americans on the experience of the rich? That is, essentially, what both of the key studies were. These populations of lawyers and business executives may have looked much like average Americans; their body weights, rates of various diseases, and dietary patterns may have been not that different from those of a lineman for the telephone company or a data processor for an insurance company. But their total life experiences were very different. What made thirty minutes of accumulated activity a prophylactic against heart disease for the rich — with their already highly buffered existence — would likely, one might surmise, be much more dilute for the middle class, even more so for the poor. This is because when the rich garden, even briskly, they are doing so with all the other health advantages that come with being rich. Their mini-dose of exercise is amplified by socioeconomics. Not so with the middle class, let alone the poor.

And what about moderate exercise over vigorous exercise, or accumulated activity over sustained, and the idea that most benefits accrue at the low end of activity increases? To what degree did those notions hold up? New reviews are increasingly calling them all into question.

Perhaps the most vexing arena of controversy involves what was the most radical part of the new recommendations — the notion that accumulated activity is as beneficial as sustained activity. This was the element of the reform plan that engendered such creative interpretations as "doing a few minutes of housework" or "intensely bowling." In the scientific literature it is known as "fractionalization of physical activity." To date, evidence for such

WHY THE CALORIES STAYED ON OUR BODIES

as an exercise prescription (rather than as an observation of activity patterns of the rich) rests largely on one single study involving thirty-six subjects. In it, eighteen healthy men completing thirty minutes of exercise training a day were compared with eighteen men completing three daily ten-minute bouts. Both exercised at a moderate rate — at about 65 to 75 percent of their peak treadmill test heart rate. The authors, led by Stanford's Robert F. DeBusk, concluded that "multiple short bouts of moderate intensity exercise training significantly increase peak oxygen intake," thereby implying that multiple rounds were as good as sustained rounds.

But closer reading leaves one wondering about that conclusion. This is because, at each and every point of comparison, the sustained group performed better than the fractionated group. Peak oxygen intake of the sustained group improved by 4.4 points, as opposed to the fractionated group, which improved by only 2.4 points. Adherence to each respective regimen was the same — thus undermining another supposed advantage of the multiple-session doctrine. The sustained group tended to complete its training session more often than did the fractionated group. As the authors themselves stated, "multiple short bouts of exercise increased peak oxygen uptake 57 percent as much as a single long bout." In other words, a bit more than half as much as the sustained group. These were, to be sure, small differences, and it was clear that the fractionated exercisers were getting more benefit than previously thought. But that was a long way from emphasizing, as the authors did, that "high intensity exercise affords little additional benefit."

What about the general notion behind the recommendations — that health benefits of physical activity are linked principally to the total amount of activity performed? Again, the latest data suggest otherwise. In a more recent work, Paffenbarger found that Harvard alumni who took up moderately vigorous sports activity significantly reduced their mortality risk from all causes compared with those who did not engage in such activity. "In

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contrast," the scholar Paul Williams has noted in a recent Archives of Internal Medicine report, which reanalyzed Paffen-barger's data, "increasing the overall daily activity had no significant impact on overall mortality." Intensity trumped total accumulated activity.

Even more recently, Williams, of the Lawrence Berkeley National Laboratory, produced a stunning series of papers that, in toto, undermine every single assumption of the 1993 recommendations. In a study of 8283 male recreational runners, he revived the old, rejected notion of a dose-response effect. As he put it, "Our data suggest that substantial health benefits occur at exercise levels that exceed current minimum guidelines and do not exhibit a point of diminishing return." In July 2000 Williams eviscerated the new doctrine again, this time by performing a meta-analysis of twenty-three fitness studies representing 1,325,004 person-years of follow-up. The result showed that the risks of heart disease decreased linearly with increasing amounts of physical activity — a clear dose-response effect. "Formulating physical activity recommendations on the basis of fitness studies," like the Cooper and Harvard projects, he concluded in the ACSM's own journal, "may inappropriately demote the status of physical fitness as a risk factor while exaggerating the public health benefits of moderate amounts of physical activity [Williams's emphasis]."

It was, of course, easy to dismiss a lone voice in the wind, which is how Williams has been greeted by the reformers. But the snickering turned stone serious in mid-2001, when the ACSM published the findings of a symposium on the subject of "dose response issues concerning physical activity and health." Looking at a number of its own studies over the years, the panel found that "overall, there is a consistent inverse dose-response relationship between physical activity and both the incidence and mortality rates from all cardiovascular and coronary heart disease." It also notes that the dose-response relationship held true for prevention of type 2 diabetes, colon cancer, and obesity.

Slowly — and quietly — the reformers have begun to recog-

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nize their errors. The ACSM itself recently published a third position statement calling for a larger volume of activity performed at higher intensities than the 1993 statement. An even more recent study, this one on diet, lifestyle, and type 2 diabetes by the Harvard School of Public Health, goes the extra distance as well. Noting that "current strategies have not been very successful, and the prevalence of obesity continues to increase," the study repeatedly clarifies and amplifies what is meant by adequate physical activity — "vigorous sports, jogging, brisk walking, heavy gardening, heavy housework — vigorous enough to build up a sweat."

The most recent round of "Dietary Guidelines" meetings also called the conventional wisdom to account. Noting that members of the Weight Registry, the only large database that tracks people who have lost weight and kept it off for three years or more, average 2825 calories of exercise a week, compared with the current 1000-calorie recommendation by the American College of Sports Medicine, one prominent member declared, "Are we being aggressive enough or are we simply setting guidelines that we hope will be more appealing to people who have not been successful?"

Canadian health authorities, which have long followed the U.S. lead, have been bolder; adults, they advise, should get sixty minutes of physical activity every day. Why? Because, as the ACSM's journal put it, "the assumption [is] that most people interpret the public health message in terms of predominantly light intensity activities, thus the necessity to recommend a larger daily volume."

Translation: People are lazy, so it does not pay to give them an out when it comes to exercise. It is better to ask for more — not less.

Yet asking for more has become anathema to health policy makers in the realm of fitness. Consider, for example, the strange story of the nation's weight control guidelines.

The guidelines are promulgated every five years by a small,

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elite group of nutrition scholars who meet at the USDA's South Agriculture building on Independence Avenue. There they discuss what might be the government's single most important public health action — issuance of the agency's twice-a-decade "Dietary Guidelines for Americans." With spiffy graphics and a multimillion-dollar publicity budget, the guidelines are supposed to communicate the state of the art in nutritional science and health recommendations. Functionally, the guidelines also serve as something else. Almost shamanically they act as the national conscience on matters of food, exercise, and weight control. Their incessant repetition on TV, on radio, in schools, and in popular fitness forums sets the mood for the nation on such issues, ratcheting up and down the guilt levels on various dietary behaviors.

By 1990 the weight control recommendations of the Dietary Guidelines Committee had already been loosened once. In 1980 the guidelines had advised Americans to "maintain an ideal weight" — a clear, unequivocal message that anyone who could read one of those omnipresent weight-for-height charts could understand. By 1985, in the middle of the supersize revolution, the advice was altered to the more vague "maintain a desirable weight," the better not to impose unrealistic goals upon an increasingly touchy populace. In 1990, even as obesity rates spi-raled upward, the committee wanted not only to loosen the weight guidelines again, it also wanted to do something it had never done before. It wanted to tell Americans that it was okay to gain significant amounts of weight as they got older.

The impetus had come from Dr. Reubin Andres, a remarkable man with a peculiar agenda. The chief of the metabolism section of the National Institute on Aging, Andres had a long and deep track record in the area of gerontology, diabetes research, and public health policy. (By the mid-1990s he would also enter the annals of medical history as the inventor of the euglycemic clamp, to date the best way to measure insulin secretion and sensitivity in human beings.) In the 1980s Andres had become ob-

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sessed with the issue of weight guidelines for the elderly. For four decades, he argued, the nation had hewn to an unnecessarily strict weight-for-height chart set down by the Metropolitan Life Insurance Company. Those standards, he said, were not only unrealistic but also unscientific; they reflected only the experience of people who could afford life insurance, a largely white, affluent, and middle-aged cohort that no longer represented the increasingly diverse country.

To prove his point, Andres performed a statistical reanalysis of what was then Metropolitan Life's most recent data, published in 1979. Also known as the Build Study, the data had become the basis for new weight-for-height recommendations issued in 1983. Andres turned a new lens on the data: What if one broke the data up into age groupings, then asked, essentially, "At what weight-for-height ranges does minimum mortality occur in each age bracket?" Andres and a few colleagues used the question to guide a reworking of the Met Life numbers. They came up with a surprising revelation. As Andres read the revised data, the Metropolitan recommendations were "too low." It was better — that is, less risky — to be fatter — up to fifteen pounds fatter — once one turned forty. This was because "the Metropolitan Life tables have erred, apparently in an effort to simplify the weight recommendations, by not entering age as a variable."