Study links decrease in U.S. workplace physical activity with obesity epidemic

In a new study conducted at the Pennington Biomedical Research Center, scientists have found that the decrease in workplace physical activity over the past fifty years is a significant contributor to the obesity epidemic.  The study suggests that changes in caloric intake cannot solely account for observed trends in weight gain increases for men and women in the United States.

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

In the 1960s, more than one half of jobs included moderate physical activity in contrast to today's less than 20 percent, according to the new study. "Yesterday's jobs have been replaced by sitting or sedentary activity.  In the last fifty 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," said lead study Pennington Biomedical scientist Timothy Church, M.D., M.P.H., Ph.D. and John S. McIlhenny Endowed Chair at Pennington Biomedical Research Center.

"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 Dr. Church.

The study examined the trends in occupational physical activities over the past five decades, comparing how the trends compare to concurrent changes in body weight in men and women in the United States.

In 2008, federal physical activity recommendations were released suggesting 150 minutes per week of moderate intensity or 75 minutes of vigorous intensity physical activity per week. However, only 1 in 20 Americans are 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.

In the study, the authors chose to focus on occupation activity as it represents the largest segment of waking hours for adults. Over the past 40 years, the workforce has also changed dramatically, with more women working today. Since 1970, the percentage of women in the workforce has risen from 43 percent in 1970 to 60 percent in 2007. These findings support the fact that a major focus on public health interventions and research in the future should be directed towards increasing physical activity outside of the workplace.