Going to work can make you fat?

Another reason to dread the ol' 9 to 5 — it can make you fat.

A study published by the journal PLoS One that followed job trends over the past 50 years found that American workers aren't working as hard as they used to. While most fingers pointed to poor diet and lack of exercise as reason for America's expanding waistline, the workplace is one facet that has been relatively ignored.

But now the eight hours Americans spend planted in front of a computer screen are facing scrutiny, especially with the rise of sedentary jobs. Researchers estimate that, compared to the 1960s, workers burn about 120 to 140 calories less per day, which coincides with the gradual weight gain that has made obesity an epidemic.

In the study, researchers point to a shift from occupations that require physical labor to more sedentary office jobs. Jobs with light or no physical activity have steadily risen since the '60s, while those with moderate intensity physical activity have dropped from 48 percent to 20 percent in 2008.

United Steel Workers health, safety and environment Director Michael Wright said that not only have manufacturing jobs diminished, but the ones that remain are also becoming more sedentary. As more power tools and mobile equipment become available, he said, operations in steel mills and chemical plants require less physical labor.

So now, instead of lifting and moving objects, workers control machines that do the work for them. The rise of technology has also made jobs with little activity even more sedentary. As computers and email become the linchpin of the workplace, even small actions such as passing on a memo have become almost obsolete.

Linda Anderson, a Franklin Park, Pa., resident who works as an office manager, said the computer has made her job even more sedentary, especially in the past decade. "We instant-message each other instead of getting up and talking," she said.

And while that might not seem like a major contribution to obesity, sports medicine physician Tanya Hagen said that the inactivity adds up.

"In the end, it's calories in and calories out," she said. Because people are burning fewer calories than in the past, they're accumulating extra calories at the end of the day. Dr. Hagen estimated that if a person has a 150-calorie surplus every day, that will cause them to gain one pound every two weeks, or about 25 pounds in a year.

Weight gain isn't the only negative byproduct of the office chair. Researchers from the University of Western Australia found that working in a sedentary job for more than 10 years may double one's risk for distal colon and rectal cancer. Although the study didn't explore why sedentary work is linked to certain types of cancer, it did say the association remains, even among those who have active lives outside the office.

(Contact Olivia Garber at ogarber@post-gazette.com.)