The myth of sloth

Did you hear how active Americans are today? Really. There is no epidemic of sloth, as we hear incessantly. The latest U.S. Centers for Disease Control and Prevention report barely made a blip on the news, but it found that the numbers of men and women engaging in “regular, moderate or vigorous activity” increased from 2001 to 2005. Among women, Hispanics and Blacks, increases have been most significant. Despite the nonstop admonitions that too many Americans are sedentary and that public health officials must do something about it, the CDC reported that about half of all adults are getting regular physical activity.

Not so fast....

The real picture is even more favorable than this report suggests. Its figures, based on Behavioral Risk Factor Surveillance System (BRFSS) surveys, are just a fraction of the numbers of Americans actually active. Many more are on the move. To learn that, however, one needs to read the report carefully, paying close attention to the wordsmithing.

Start with the phrase “regular, moderate or vigorous activity.”

According to the CDC editors: “The survey questions were not designed to assess whether a combination of moderate and vigorous physical activity met the requirement for engaging in regular physical activity when the two activity types measured separately did not; therefore, prevalences might have been underestimated.”

In other words, someone who went to an intense aerobics class two days a week and took walks for three other days that week, would not have met their definition for regular activity because they didn’t do sufficient vigorous exercise that week (at least 20 minutes a day three or more days a week) or sufficient moderate exercise that week (at least 30 minutes of moderate activity 5 or more days a week) to count.

Next, look closely at how “activity” is defined. The BRFSS survey asks only about leisure time activity — activity engaged in “when not working.” That does not mean that those without abundant leisure time to exercise are not active — but for this survey, activity done in the course of a workday doesn’t count.

So, a housekeeper, construction worker, gardener, delivery person, store stocker, medical worker, handyman, rancher/farmer, nurse, and even that aerobic instructor who moves practically nonstop all day would not be considered active. Their activity isn’t during leisure time to count.

Similarly, even if you believe people overstate their activities on anonymous surveys, they are also likely to underreport healthful activity. If it’s not ‘exercise’ many people don’t think of what they do as physical activity and report it. Also, to assess vigorous activities, for example, the survey asks about running, aerobics, heavy yard work, or anything that causes large increases in breathing or heart rate. But the most careful research has found it takes considerably less activity than is popularly believed to get health benefits, making intensity a problematic measure of health outcome.

Finally, the people surveyed in the BRFSS are increasingly not representative of Americans and the methodology is likely to underestimate activity levels. Only those with land line phones are included in the survey population, and only about half of those contacted have time to answer their lengthy questions and agree to participate. Those people on the go, younger and of higher socioeconomic status are more likely to use cell phones and not be included in the survey. BRFSS data is more apt to measure people who are poorer, unemployed, housebound, disabled or elderly, or sitting at home.

In other words, it’s skewed towards those more likely to be sedentary and to underestimate the numbers actually active — which makes the increases and large numbers regularly engaging in government-defined levels of activity in their spare time even more remarkable.

Looking at longer trends, one would anticipate that with the aging of the population (levels of physical activity generally decline among those of advanced ages), that we would expect to see levels slowly ebbing, but that’s not the case at all. This report showed that levels increased between years 2001 and 2005 to 49.7% and 46.7% among men and women, respectively. Previous BFRSS surveys have reported on levels of inactivity and reported that 31.5% of Americans were supposedly inactive in 1989. Inactivity dropped to 29.7% in 1994 and dropped again to 23.7% in 2004 — during all of those years ‘obesity’ rates were reported as soaring, by the way.

The National Health Interview Surveys from the CDC’s National Center for Health Statistics, which asks slightly different questions, has also shown that the numbers of us getting regular physical activity rose from 1998 to 2005.

The government’s own evidence doesn’t support fears that we’re a nation of couch potatoes or that sedentary behaviors are a new public health crisis and in need of massive national fitness agendas and “active living” initiatives to mandate active behaviors. In fact, the government’s own data shows our health and lifespans continue to improve to the highest levels in our history. People are doing a pretty good job taking care of themselves. Good news travels slow...