Lead study author Dr. Timothy Church of the Pennington Biomedical Research Center in Baton Rouge, La., says in the 1960s more than one-half of jobs required some type of moderate physical activity, but today workplace physical activity is less than 20 percent.
"Yesterday's jobs have been replaced by sitting or sedentary activity. In the last 50 years, we estimate that daily occupation-related energy expenditure has decreased by more than 100 calories per day, and this reduction accounts for a significant portion of the increase in mean U.S. body weights for women and men," Church says in a statement.
In 2008 the federal government recommended adults do 150 minutes per week of moderate intensity or 75 minutes of vigorous intensity physical activity per week.
However, only one in 20 Americans are meeting these guidelines, but had Americans followed the recommendation, this would make up for the decreased activity levels in the workforce, Church says.
The findings are published in the journal Public Library of Science.