A new study by University of North Carolina at Chapel Hill researchers finds a global decline in activity levels and predicts a continuing rise in inactivity in countries around the world. When viewed in the context of physical activity levels throughout human evolution, the global decline in physical activity in just the past few decades is particularly abrupt.
The study, conducted by Barry Popkin, Ph.D., W.R. Kenan Jr. Distinguished Professor of nutrition, and Shu Wen Ng, Ph.D., research assistant professor of nutrition, both at UNC’s Gillings School of Global Public Health, used extensive data from the 1960s onward to determine how people around the world spend their time and how they move in the course of their daily lives. The resulting publication, “Time use and physical activity: a shift away from movement across the globe,” appeared online in Obesity Reviews Early View Section today and will be published in the August issue (Obesity Reviews Volume 13 Issue 8 August 2012). Obesity Reviews is an official journal of the International Association for the Study of Obesity.
“We have understood for some time that children and adults in the United States are increasingly spending more time in front of televisions and in other sedentary activities such as playing computer games, using computers and texting on cell phones,” said Ng, who is the study’s senior author. “This study shows that the same shifts have also occurred in China, India, Brazil and the United Kingdom. In fact, we find adults in the U.K. are more sedentary than those in the U.S.”
Popkin noted that the introduction of home technology that includes rice cookers, refrigerators, stoves, washing machines and microwaves is global, reducing the time traditionally spent producing food and completing housework. Similar technological changes have led to less walking, more use of cars and buses, and in general, have lowered activity spent in travel across the world.
Historically, Ng said, adults have been most active in their jobs. Now, she says, “whether you live in China, India or the U.S., computers and many forms of automation remove physical exertion at work. Changes in the types of work people do have greatly reduced our overall activity levels over the past half-century.”
The study uses repeated nationally representative studies on time-use from the United States, the United Kingdom and China, along with more limited nationally representative time allocation data from Brazil and India, to document very rapid declines in physical activity. This is particularly true in China and Brazil, the countries with the two highest absolute and relative rates of decline in total physical activity and some of the higher increases in sedentary time.