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 ReviewsVolume 13 Issue 8 August 2012). Obesity
Reviews is an official journal of theInternational 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.
For
these two countries, declines in activity were driven largely by reductions in
movement at work, at home, and to a lesser degree, in travel or transportation.
This is not surprising given that in the past few decades, the Chinese and
Brazilians have been shifting away from agriculture into manufacturing, service
and other sectors, increasing use of machines and labor-saving technology in
the workplace, and acquiring greater access to home technologies (e.g.,
electrification, piped water, appliances), as well as motorized vehicles.
The
study makes projections, given continuation of the current trends, for the
levels of activity in the five countries in 2020 and 2030. The forecasts are
bleak. Using a physiological measure called metabolic equivalent of task (MET),
which describes the amount of energy spent in accomplishing a task, the study
determined that by 2020, the average American adult will expend about 190 MET
hours per week. In comparison, a person who slept 24 hours in a day would
expend 151 MET hours per week, and an active adult who did vigorous activity
for 30 minutes to an hour every day, but otherwise had a desk job, would expend
between 240 and 265 MET-hours per week.
People
in Britain will reach the 190 MET hours level by 2030. Those in China and
Brazil will continue on a steeper downward trend, reaching the U.S. and U.K.
physical activity levels by 2030. The situation in India appears less severe,
but the average of the levels masks the stark socioeconomic dichotomy likely to
continue in India, with wealthier Indians leading lifestyles similar to those
of the British.
These
changes will have significant implications for health outcomes, health-care
costs, and overall functional well-being of societies around the world. In
addition, it is important to note that how we move has a great deal to do with
global health, human development and well-being Physically active children
learn better, active adults live longer and are more functional and active
women are less prone to osteoporosis and bone fractures.
By
focusing on these five countries, which represent more than 3 billion
individuals (nearly 50 percent of the world’s population), this study presents
what can be expected if no action is taken to curb rapid declines in physical
activity and increases in sedentary behavior.
The
study authors call for global initiatives and advocacy efforts in all
regions of the world to build momentum to study and effectively intervene in
all domains of movement. Given the material impact that physical
activity has on health, human development and national well-being, Popkin noted
“one of the most important activities for governments to undertake going
forward is to start to measure population-wide physical activity levels.
In particular, long-term investments to create a publicly accessible, worldwide
physical activity standard would be a significant advancement for the field.”
“Our
hope is that this multicountry study will spur global action to reduce
sedentary behavior and increase activity across multiple domains of daily
activity,” Ng said. “Being active throughout our daily lives and across the
life cycle is important in terms of human development, health outcomes and
economic productivity.”
More
information: http://dx.doi.org/
… 2011.00982.x
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