Monday, October 05, 2020

Most Americans Don't Get Enough Exercise: True or False?

There's a lot of tsk-tsking about how little exercise Americans get, with many blaming our couch potato lifestyle for our growing girth. Now this notion is being called into question by a CDC study that probes more deeply how much exercise the average person gets in a typical week. 

First, a little background. The federal government measures our physical activity through the National Health and Nutrition Examination Survey (NHANES). The survey asks respondents how much moderate/vigorous leisure-time physical activity they get in a typical week. Over the years, the survey has consistently found a minority of adults meeting the government's guideline of 150 moderate-intensity minutes of physical activity per week. Only 38.6 percent met the aerobic guideline in 2011–16.

But wait. All this time, the government has been counting only leisure-time physical activity. So all the sweat and tears of those who move furniture, hammer nails, dig ditches, chase toddlers, clean houses, and turn patients don't count. Until now. The CDC added additional questions to the 2011–16 NHANES asking about physical activity during paid work, housework, and transportation (walking to the store, biking to work). Voila! When those domains are also considered, the 64 percent majority of adults meet the aerobic guideline. Not only that, but some of the exercise disparities between groups narrow. 

Take education, for example. When measuring only leisure-time physical activity, the percentage who meet the aerobic guideline ranges from a low of 22 percent for the least educated (without a high school diploma) to 53 percent among the best educated (with a bachelor's degree)—a 31.2 percentage point gap. But when physical activity during paid work, housework, and transportation are added to the mix, the gap is cut in half. The 54.6 percent majority of those with the least education now meet the guideline compared with 69.1 percent of college graduates, a 14.5 percentage point gap. 

When all domains are considered, the majority of Americans in all but one demographic segment meet the federal guideline for aerobic physical activity during a typical week. People aged 65 or older are the only ones who fall short, with 46.5 percent meeting the guideline (up from 27.3 percent when only leisure-time physical activity is considered). Why doesn't the federal government always include the other domains when it asks about physical activity? Because doing so would add questions to the survey and increase respondent burden, the CDC notes. 

The fact that Americans get more exercise than long assumed is good news. But there's bad news as well. If most Americans are meeting the aerobic physical activity guideline, then something other than a lack of exercise must be to blame for our increasing weight. Time to start skipping dessert.

Source: CDC, Combining Data form Assessments of Leisure, Occupational, Household, and Transportation Physical Activity among Adults, NHANES 2011–2016

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