Our sedentary jobs.
Only 6.5 percent of adults meet guidelines for physical activity while at work, according to one of the studies, published in the May 27 issue of Morbidity and Mortality Weekly Report. That study was echoed by another showing that only 20 percent of Americans have jobs that require moderate physical activity, down from 50 percent in 1960.
The authors of the second study, which was published in the May 25 issue of the journal PLoS ONE, estimate that today's cubicle-dwellers burn 140 fewer calories at work each day than our clock-punching counterparts did a half-century ago.
But if Americans aren't working up a sweat sitting at our work computers, we seem to have no trouble working up an appetite.
From vending machines down the corridor to fast food down the block, "We have opportunities to eat all day, and we're doing it," Dr. Barbara Rolls, professor of nutritional sciences at Pennsylvania State University, told USA today.
What's the way to shrink this growing problem?
"If we're going to try to get to the root of what's causing the obesity epidemic, work-related physical activity needs to be in the discussion," study author Dr. Timothy S. Church, professor of preventive medicine research at the Pennington Biomedical Research Center in Baton Rouge, La., told the New York Times.
In addition to talking, we need to get moving, said Dr. Ross C. Brownson, professor of epidemiology at Washington University in St. Louis. "We need to think about physical activity as a more robust concept than just recreational physical activity," he told the Times. "In many ways we've engineered physical activity out of our lives, so we've got to find ways to put it back into our lives."
So instead of simply heading to your sofa - or even a gym - after work, Brownson suggests taking walks during breaks at work or finding other opportunities for exercise all day long.
Time to get up out of your swivel chair?