A lot has happened since 2008. In that time, athletes have competed at five more Olympic games, the first licenses for driverless cars were granted in the U.S., and Americans have elected two different presidents. Unfortunately, we've also experienced a steady rise in the obesity rate in the U.S. from 33.7% in 2008 to 39.8% in 2016.
This upward trend is alarming because people becoming more obese—and sedentary—across America has substantial consequences. "We can attribute 10% of all-cause mortality in the United States to not doing enough physical activity and $117 billion in healthcare costs," says Katrina Piercy, Ph.D., RD, ACSM-CEP and lead for the 2nd Edition of the Physical Activity Guidelines for Americans, which was released by the Department of Health and Human Services in November 2018.
The new guidelines have not changed the amount of physical activity someone should get in a day—that magic number is still 150 minutes a week for adults and 60 minutes a day for kids under 17 years old. But the new guidelines do expand what can count towards activity. In short, they encourage people to move more and sit less. The thinking is that doing something—even light activity—is better than nothing. Of course, moderate to vigorous physical activity is still ideal.