It is well known that the obesity rates in the United States have increased in recent years. Several common causes for this trend continue to receive media attention, including increased caloric intake (especially unhealthy foods such as fast food) and the small percentage of Americans who participate in moderate- to vigorous-intensity physical activity during leisure hours. However, a new study by Timothy S. Church et al. suggests that our jobs might be to blame for the obesity epidemic.
In the May 2011 Issue of PLoS ONE, the authors present their results from a study looking at the changes in the workplace in terms of types of jobs performed by the American workforce. They then computed the decrease in daily energy expenditure in these jobs. They used these numbers to create a model to predict expected weight gain and then compared it to actual data of Americans throughout this period.
The data is unfortunately convincing. Over the last five decades, there has been a large decrease in goods producing and agricultural jobs while there has been a large increase in service occupations. For example, while construction has been fairly constant, manufacturing and mining/logging occupations have decreased tremendously. Meanwhile, professional services, health/education, and leisure/hospitality occupations have dramatically increased.
When the types of jobs are classified as sedentary, light intensity, or moderate intensity, the authors found that the prevalence of moderate-intensity physical activity occupations dropped from 48% in 1960 to 20% in 2008. Using a model that estimated metabolic equivalents based on physical activity intensity of the categories of occupations, they estimated a decrease in energy expenditure at work of 140 calories per day for men and 124 calories per day for women. Finally, inputting these numbers into an energy balance model, this daily decrease in energy expenditure at work predicted weight gains that correlated well with actual weight gains seen in each decade by the National Health and Nutrition Examination Surveys.
While I would not dismiss a lack of moderate-intensity physical activity during leisure time (as I have written about for both adults and children), the authors do point out that the time Americans spend in leisure time activities has remained fairly steady. Leisure activity also makes up a small percentage of the total number of hours in a week. And Church is quick to note that meeting the 2008 Physical Activity Guidelines for Americans would erase the greater than 100 calorie per day decrease in work energy expenditure.
I think that there are several key points to learn from this study. Obviously if we are not burning calories at work, then we need to get exercise outside of work. Only 1 in 4 Americans perform 150 minutes of moderate-intensity physical activity or 75 minutes of vigorous-intensity physical activity per week. As the authors point out, only 1 in 20 Americans meet these guidelines when accelerometers are used to measure activity. These numbers just have to improve. Church argues, “…since energy expenditure has largely been removed from the work place the relative importance of leisure-time physical activity has increased and should be a major focus of public health interventions and research.”
I also don’t think we should give up on our jobs as wasted time in the sense of calorie burning. I realize that a large percentage of us work at desks. (In fact, I bet that many of you are reading this article at work.) But doing a sedentary job doesn’t mean that you have to be confined to your desk. Try a few simple ideas to burn those 100+ calories:
1. Park toward the back of the parking lot to increase the distance you walk entering and leaving the building.
2. Use the stairs instead of the elevator.
3. If you have a work issue that will involve back-and-forth emails to a colleague in the office, skip the emails and walk to his or her office to discuss it.
4. Walk to a nearby restaurant (preferably one that offers healthy choices) rather than eating in the cafeteria at work.