Researchers at the University of South Carolina's Arnold School of Public Health have validated a new method for calculating physical activity, sedentary behavior, and the food energy requirements of Americans. The results suggest that as a nation, we spend more than 15 hours per day sleeping and sitting, and that obese men and women spend less than one minute per day in vigorous activity.
The study, led by Arnold School exercise scientist and epidemiologist Edward Archer and published in the journal Mayo Clinic Proceedings, used accelerometry based technology to validate a protocol for calculating energy expenditure and food energy requirements. The study of the Physical Activity Ratio (PAR) protocol is significant because it provides the first nationally representative estimates of total daily energy expenditure, physical activity and sedentary behavior for the U.S. population.
"In the past, physicians and researchers used questionnaires to obtain estimates of lifestyle factors such as physical activity, exercise, sedentary behavior, and diet," Archer said. "Unfortunately, this method rarely provided accurate or reliable data, and without valid estimates, public health policy and food-based guidelines are ineffective and/or counterproductive."
"Conventional wisdom and research over the past five decades suggest that obese men and women engage in less physical activity than normal weight individuals," Archer said. "With results from this study taken into account, and the overwhelmingly sedentary nature of the current U.S. population, the message to 'move more, sit less' is sound, empirically supported advice that is easily understood by health care professionals and the public."
Data sets for the study were obtained from the National Health and Nutrition Examination Survey 2005-2006, a complex sample of the U.S. population conducted by the Centers for Disease Control and Prevention, and included adults age 20 to 74. The sample population was then divided into three Body Mass Index (BMI) categories: normal weight (18-25 kg/m2), overweight (25-29.9 kg/m2) and obese (30 kg/m2 or more) and took into account all factors contributing to energy expenditure, including sleep, and the digestion and metabolism of food.
The study found that the 1,272 men and 1,325 women that comprised the final sample exhibited key differences based on sex and BMI. Men were taller, heavier, and had greater resting energy expenditure than women. Men also spent more hours per day engaging in moderate and vigorous physical activity, and reported less sleep.
Not surprisingly, obese men and women were significantly less physically active and spent more time in sedentary behaviors than their normal weight counterparts. Obese men and women also reported less sleep and spent almost no time in more intense forms of physical activity. "Given that physical inactivity is now a leading cause of death and disability in the world, these data are essential in advancing the science of obesity and health," Archer said.
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