A drop in workplace physical activity over the past half century has helped propel rates of U.S. obesity to among the highest in the world, a study said.
Less than 20 percent of jobs now require at least moderate exertion, a drop from almost half of all private-industry jobs five decades ago, according to research published yesterday in the journal PLOS One. The change in job-related daily physical effort matched the actual change in weight for some.
“Over the last 50 years in the U.S. there has been a progressive decrease in the percent of individuals employed in occupations that require moderate intensity physical activity,” the study said. The reduction in energy expenditure “accounts for a significant portion of the increase in mean U.S. body weight for women and men over the last five decades.”
More than a third of U.S. adults, or over 72 million people, are obese, according to the Centers for Disease Control and Prevention in Atlanta. The obesity rate has doubled for adults between 1980. Obesity increases the risk of type 2 diabetes, heart disease, and some cancers, according to the CDC.
The researchers analyzed occupational data from the U.S. Bureau of Labor Statistics and compared it with mean body weights from the U.S. National Health and Nutrition Examination Surveys. They found that predicted weights based on change in occupational-related daily energy expenditure since 1960 closely matched the actual change in weight for 40- to 50-year-old men and women.
The number of calories expended by U.S. workers had dropped on average by more than 100 in the period, said the researchers, led by Timothy S. Church and Claude Bouchard at Louisiana State University in Baton Rouge.
Service occupations, which are less strenuous than manufacturing and agriculture, now account for 43 percent of U.S. private-sector jobs, compared with 20 percent in the early 1960s. The study didn’t factor in technological changes that make manufacturing and agriculture easier, meaning that the study may be underestimating the trend, the researchers said.