Obesity linked to decrease in physical activity in workplace

Warning: Your workplace may be making you fat.

A new study has found that the decrease in workplace physical activity over the past 50 years is a significant contributor to the obesity epidemic.

Dr. Steve Blair, a researcher with USC’s Arnold School of Public Health and one of the study’s co-authors, said the study underscores that changes in caloric intake are unlikely to fully explain the epidemic of overweight and obesity observed over the past 30+ years for men and women in the United States.

The study, "Trends Over 5 Decades in U.S. Occupation-Related Physical Activity and their Associations with Obesity," was published May 25 by the Public Library of Science (PLoS), an international peer-reviewed journal in science and medicine.

Researchers from the Pennington Biomedical Research Center, Montclair State University and the Arnold School of Public Health analyzed data from the U.S. Bureau of Labor Statistics on energy expenditure for occupations in the nation’s private industry since 1960. They also studied mean body weight from the U.S. National Health and Nutrition Examination Surveys (NHANES), as well as data from the U.S. Bureau of Labor Statistics and U.S. Census Bureau.

In the 1960s, more than one half of jobs included moderate physical activity. That number has dropped to less than 20 percent today, Blair said.

"We only have to look around to know that many jobs in today’s workplace primarily involve sitting and little movement. This is clearly the norm, compared to jobs of the past that required more physical activity,” said Blair, who is on the faculty in the Arnold School’s department of exercise science and department of epidemiology and biostatistics.

The researchers estimate that daily occupation-related energy expenditure has decreased by more than 100 calories per day – a finding that is likely a major contributor for the increase in body weight for women and men.

"The causes of the obesity epidemic are a hotly debated issue, particularly in regard to the relative importance of diet and physical activity. Our data provides further support to the importance of including both diet and physical activity in discussions related to be both the causes and potential solutions of the on-going obesity epidemic," said the study’s lead author Dr. Tim Church, a researcher at the Pennington Biomedical Research Center.

Federal physical activity recommendations, released in 2008, recommend that American adults get 150 minutes per week of moderate intensity or 75 minutes of vigorous intensity physical activity per week. However, many Americans are not meeting these guidelines. If men and women were meeting these recommendations, this would make up for the decreased activity levels in the labor work force, the researchers said.

The researchers focused on occupation activity as it represents the largest segment of waking hours for adults. Over the past 40 years, the workforce has changed dramatically. Since 1970, the percentage of women in the workforce has risen from 43 percent in 1970 to 60 percent in 2007.

“The study helps us understand that energy expenditure is much less in the workplace today than 50 years ago,” Blair said. “Therefore, the importance of physical activity in leisure time and spending less time sitting should be a major focus of public health inventions and research.”