1. No category

PRACTICE APPLICATIONS
Topics of Professional Interest
What Is Sedentarism?
O
NE OF THE MORE PROMINENT
warning labels in the modern
consumer world reads as
follows: “SURGEON GENERAL’S
WARNING: Smoking Causes Lung Cancer, Heart Disease, Emphysema, and
May Complicate Pregnancy.” It is a
harsh caution, but smoking cigarettes
has proven to be so dangerous to one’s
health that the government forces cigarette companies to advise potential
customers against using their very
merchandise. A warning of this magnitude is clearly reserved for products
that are extremely harmful and very accessible to the public. Therefore, if
there existed a product that was potentially as harmful as, and certainly more
ubiquitous than, cigarettes, clearly it
too would be worthy of such a warning.
However, this new warning may come
from some unlikely sources— office
chairs and living room couches.
It may be difficult to believe, but a
recent study proposes that remaining
seated—sedentary—for long periods of
time may be just as dangerous as smoking.1 Considering the stigma that is associated with smoking, both by health
care professionals and the public, this
claim may seem difficult to reconcile
with preconceived notions. But research is beginning to reveal the serious health risks of engaging in sedentarism, or sedentary behavior, and
indicates that it may function as an important predictor of future health in a
similar capacity as diet, exercise, and
harmful habits such as smoking.
Sedentarism is a term that is likely to
be met with presumed understanding as
the opposite of being physically active, or
engaging in insufficient amounts of moderate-to-vigorous physical activity (MVPA;
exercise). This line of thinking, however,
may be incorrect; mounting evidence
shows that sedentarism should be
thought of as a distinct issue from a lack
of dedicated exercise. Studies indicate
that sitting too much is different from
exercising too little,2 and the consequences of excessive sitting are equally
detrimental.
With sedentarism becoming more
prevalent the world over, it seems prudent to afford this health concern some
genuine contemplation.
DEFINITION
The idea of sedentarism being conceptually distinct from a lack of dedicated
exercise is bound to cause some confusion. Common perception is that exhibiting sedentary behavior is essentially
the lowest end of the spectrum of physical activity. It is becoming increasingly
acknowledged, however, that sedentarism requires a definition separate from
MVPA.
The term sedentarism refers to the
many of the “activities” commonly associated with the word sedentary—sitting, lying down, sleeping, and the various actions that are often performed in
these states of low energy consumption, such as watching television (Figure 1).3 On their own, these are lowenergy activities; when accumulated
into in prolonged periods or a lifestyle,
they represent sedentary behavior.
Someone who includes a high amount
of these low-energy activities in dayto-day life can be characterized as exhibiting sedentary behavior.4
Separating “lack of exercise” and “excessive sitting” becomes more important as the topic becomes more com-
This article was written by Matthew
Fox, a freelance writer in Hoffman
Estates, IL.
doi: 10.1016/j.jand.2012.06.018
1124
Figure 1. Common examples of sedentary activities.
JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
plex. Research during the past 10 years
has attempted to differentiate these
ideas on a technical level. An Australian
study from 2008 reported an unfavorable association between time spent
watching television and waist size,
blood pressure, and blood sugar in a
group of physically active adults who
engaged in at least 150 minutes of
MVPA per week.2 Per most guidelines,
this level of activity is sufficient to meet
the threshold where adults begin to see
notable health benefits, which includes
reduced or stable waist circumference,
blood pressure, and blood sugar.2 Excessive sitting time not only negated
the benefits of true exercise, it actually
appeared to worsen the overall health
of the test group. These findings represent a significant deviation from the
generally accepted notion that a certain
amount of MVPA will suffice as a preventative, activity-based health measure, and signify that sedentarism
should be considered separate from
lack of exercise.
The study presents an interesting
contrast to conclusions drawn only a
decade earlier. A 1999 issue of the
American Journal of Public Health published a study that, among other objectives, sought to provide a definition for
the term “sedentary” as it pertained to
classifying individuals. The authors came
to recommend that a person who expends less than 150 kcal/day in moderate
or high intensity activity (ie, exercise)
should be defined as sedentary.5 This interpretation of sedentary behavior emphasizes a definition that is too inclusive, suggesting that the difference
between “excessive sitting” and “lack of
exercise” is a matter of semantics
rather than science. Although these results are functional as part of the basis
for physical activity guidelines, usage of
the word “sedentary” in such a context
is one of the reasons why sedentarism
is at times misunderstood today.
Because sedentarism is a term that is
closely tied with physical activity, developing a unique definition is partially
a process of elimination to determine
what it is not. It is not necessarily the
© 2012 by the Academy of Nutrition and Dietetics.
PRACTICE APPLICATIONS
implication of a lack of exercise; it is not
avoided merely by meeting exercise guidelines; it is not simply explained by assigning it a minimum level of daily energy
expenditure. Beyond that, sedentary
behavior connotes prolonged periods of
sitting or overall inactivity, and this inactivity may cause or exacerbate symptoms of
metabolic syndrome independent of a lack
of dedicated exercise.3 The definition of
sedentary behavior will continue to evolve,
as more in-depth research is conducted on
the recently differentiated concept.
RESEARCH OVERVIEW
When it comes to developing a fuller
understanding of sedentarism, it is research that will guide dietetics practitioners, both in individual advice for
patients and in community-wide recommendations. The research that has
been conducted during the past decade
or so has explored a variety of hypotheses concerning sedentary behavior,
ranging from physiologic functions and
medical risks to its social determinants.
Physiology
A 2008 review from Current Cardiovascular Risk Reports emphasizes the terms
“inactivity physiology,” which refer to
the unique physiologic responses of the
body in the presence of significant lack
of physical activity.2 In addition to
highlighting the necessity of a definition of sedentary behavior separated
from “lack of exercise,” it serves as an
overarching label for further study in
the field. One objective study from the
National Health and Nutrition Examination Survey based on step-counting
accelerometers indicated that more
than half of US adult waking hours are
spent sedentary.2 A similar 2011 study
from the British Journal of Sports Medicine breaks down waking hours into
three types of physical activity—MVPA,
light-intensity physical activity (LIPA),
and sedentary time. LIPA is a term generally used to describe “background”
physical activity; that is, physical activity that is not dedicated vigorous exercise, but largely derived from everyday
tasks such as walking to a car in a parking lot or mowing the lawn. The daily
distribution of time in these three types
of physical activity is familiar: 0.7 waking hours are spent in MVPA, 6.5 waking hours are spent in LIPA, and the remaining 9.3 waking hours are spent
sedentary.4 Together with the National
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Health and Nutrition Examination Survey results and the Australian study
referenced earlier, these studies indicate that additional emphasis should be
placed on sitting less. Even without the
benefit of further examination, it is
clear that a disproportionate amount of
time for adults is spent in a state of very
low energy expenditure.
Less clear than the prevalence of sedentarism is the material effect it may
have on the body. As such, a considerable amount of sedentarism research is
directed at discovering and clarifying
potential health consequences. Accelerometers have been seen as aids in
gathering objective observational data
on the prevalence and degree of sedentary behavior, but a more active experiment involving step measurement was
discussed in a reprinted 2008 research
letter in the Journal of the American
Medical Association. In this study, a
group of healthy, nonexercising men
was asked to reduce daily steps from
between 6,000 and 10,000 steps a day
down to fewer than 1,500 steps/day for
2 and 3 weeks.6 The steps pertain to average walking activity in everyday life,
a common form of LIPA. By the 2-week
point of the experiment, there was a
marked increase in plasma insulin level
(indicating increased insulin resistance), triglycerides, and intra-abdominal fat mass.6 High levels of these
physiologic markers correlate to type 2
diabetes and cardiovascular disease,
the deleterious effects of which need
little explanation. One of the most remarkable results of this study is observing how rapidly the body begins to
transform—in only 2 weeks, with no
change in diet and level of MVPA—the
bodies of these otherwise healthy men
suffered considerable degradation.
Other studies suggest that more significant, lasting metabolic deterioration
may occur in just 6 months of sustained
inactivity.7 Research indicates that
there is no real “acceptable amount” of
prolonged physical inactivity, as it
takes relatively little time for health
consequences to manifest.
Another study examined a broader
range of adult subjects (both sexes, 18
to 98 years of age, physically active and
sedentary) and found almost unequivocally that body fat mass index, percent
body fat, and fat-free muscle index
were negatively impacted from a sedentary lifestyle.8 Age and sex normal-
JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
ization aside, a strong association was
found to exist between low levels of
physical activity and these health predictors. Cris Sletnz, PhD, exercise physiologist at Duke University, thinks the
effects of a sedentary lifestyle may be
especially insidious: “There is some
suspicion that almost every organ in
your body gets worse when physical
activity is too low.” Research on sedentarism emphasizes the surprising degree to which physiologic systems begin to deteriorate due to excessive
sitting.
Ultimately, there is no more effective
way to impart the potentially dire
health consequences of sedentarism
than by understanding how it impacts
mortality. In 2010, the American Journal
of Epidemiology published a study that
examined the statistical relationship
between leisure time spent sitting and
total death in a sample size of more
than 100,000 American adults during
the course of more than 14 years.9 The
results were grim, but unsurprising. Researchers found that sitting time was
associated with increased risk of death
(from any cause), regardless of physical
activity levels, but that there was a significant association between time spent
sitting and death from cardiovascular
disease.9 Mortality rates were roughly
25% lower among the most-active adults
compared with the least-active adults,
although mortality rates were also significantly lower even in the second lowest
category of physical activity vs the lowest. This suggests that fairly low amounts
of movement will begin to offset some of
the dangers of excessive sitting.9
The results appear consistent across
research—sedentary behavior is now
associated with physiologic deterioration, disease, and death. Even with an
increased research emphasis on sedentarism, there is still much to learn about
this increasingly unique “inactivity
physiology.” For example, the physiologic effects of sedentarism may differ
between children and adults, as new
evidence indicates that children might
benefit from MVPA regardless of sedentary time.10 Another study suggests a
different response between sexes.
Women who sit for long periods of time
show increased risk of type 2 diabetes,
whereas men do not.11 Scientific understanding of the physiologic aspect of
this phenomenon will grow as research
August 2012 Volume 112 Number 8
PRACTICE APPLICATIONS
continues, but even now the dangers of
sedentarism have never been clearer.
Social Determinants
If the research on the physiologic aspect
of sedentarism explains the “what” and
“how” of the term, then research on its
social determinants attempts to explain
the “why.” Some of the reasons are apparent by observation of everyday life.
In the developed world, travel is now
largely conducted via car or public
transportation, making purposeful
walking less necessary.12 Modern occupations require less manual activity
and are often sedentary, which, in combination with increasing leisure time
sedentary behavior, means adults are
sedentary the greater part of the day.13
Many household tasks have become
automated, which allows for the replacement of certain domestic physical
activities with less physically taxing
leisure time pursuits.12 These determinants are largely functions of the environment in which they form. Efficient,
low-energy travel options, less manually-intensive work, and conveniences
in the home are, in a sense, part of the
natural progression of society and technology. People in the United States and
other developed countries have less
need for physical activity when it
comes to meeting social and financial
responsibilities, so they abstain.
Of particular concern are occupational sedentarism and leisure time
sedentarism, as work and recreation
compose the majority of the waking
hours of a US adult. During the past 5
decades, there has been a stark decrease in the amount of US workers employed in jobs that require moderate
physical activity, which are mainly
goods producing or agricultural jobs. In
the early 1960s, nearly 50% of all jobs
required moderate physical activity,
whereas that number decreased to less
than 20% of all jobs in 2008.14 At the
same time, there has been a notable increase in jobs that require light physical
activity and jobs that are considered
sedentary, which include jobs in the
service industry (eg, trade, information,
professional, business). Light physical
activity and sedentary jobs now comprise the majority of employment of
working US adults.14 These trends have
led to a decrease in daily occupational
energy expenditure of more than 100
calories between both men and women
August 2012 Volume 112 Number 8
since the early 1960s.14 Considering the
general movement of the developing
world toward more integrated, more
convenient technology, the direction of
the statistics is unlikely to reverse.
There is, however, some resistance to
the idea that current US workers are
necessarily bound to their chairs. Companies such as Google and Facebook
offer their employees the option of
working at standing desks, and many
choose to use that option.15 In addition,
JustStand.org is a website that is dedicated to explaining the effects of sedentarism, particularly as it pertains to the
workplace, while offering ideas and
recommendations for reducing sitting
time (which include links to products
such as standing desks).16 It is encouraging that, if nothing else, sedentarism
is a phenomenon that is gathering attention in some of the places it most
acutely affects.
Of course, there is more to the day
than work, and people are increasingly
engaging in leisure time activities that
expend little energy. Television viewing in particular is an activity frequently associated with sedentarism,
and there have been studies aimed at
determining some of the specific effects
of “screen time.” Sitting for an excessive amount of time in front of a television screen is a concern for all ages, but
one study examined childhood and adolescent television viewing as a predictor for adult health.17 The choice to
study children and adolescents in this
context is useful, as unhealthy lifestyles
may actually be established by the
teenage years.18 Unhealthy childhood
lifestyles are especially interesting
from a social perspective because they
are almost purely functions of social
environment, as children usually lack
the autonomy of lifestyle choice that
adults typically possess. Findings in this
study associate the presence of significant screen time in children and adolescents with overweight, high cholesterol, and poor overall fitness through
childhood and continuing into adulthood.17
Because of findings like these, in addition to increasing rates of childhood
obesity, “there is a big push to get children away from the screen,” says
Courtney P. Winston, MPH, RD, assistant director of Nutrition Services at
Kaiser Permanente San Diego. The success of such a directive is largely in the
Figure 2. Low-impact physical activities
to break prolonged sedentary time.
hands of parents since, as Winston suggests, “When parents limit screen time,
their children tend to be more physically active.” And when television
viewing (and subsequently sitting) is
restricted, both children and adults are
more likely to engage in physical activity.
There is a significant negative correlation between sedentary time and
LIPA—as one sits less, he or she moves
more.2 Teaching quality lifestyle
choices to children that will grow with
them to adulthood takes a concerted effort of not only parents, but schools,
neighborhoods, and entire communities. Schools that promote physical activity help to encourage further physical activity in children away from
school, and neighborhoods that have a
low degree of deprivation (through
higher socioeconomic status) usually
have more facilities that promote physical activity, as well as a more favorable
appearance that is conducive to outdoor physical activity.19 And whereas
the power of these social influences is
strongest in childhood, adults show a
similar positive reaction to many of the
same community-scale factors.20 Recent
research has made significant strides in understanding the social determinants—the
“why”— of sedentary behavior, but the
potential causes will continue to develop,
change, and be further understood as
time goes on.
RECOMMENDATIONS AND THE
FUTURE
As important as it is to define sedentary
behavior and continue researching it, it
is only as useful as the information it
provides to practitioners in the field.
Fortunately, there is practical advice to
be derived for dietetics practitioners
and other members of the health care
community. For instance, there is evidence suggesting beneficial associations with breaks in sedentary time
(Figure 2). Regardless of the total time
JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS
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PRACTICE APPLICATIONS
spent sedentary per day, waist circumference and cholesterol, among other
physiologic markers, were significantly
reduced in the presence of frequent
breaks from prolonged periods of inactivity.21 The “intensity” of the breaks is
less important than the simple act of
performing any physical activity. To patients who are sedentary and looking
for small ways to improve themselves,
a dietetics practitioner might stress the
importance of breaking up prolonged
periods of sedentary time in any way
possible. Something as relatively easy
as standing up is better than the alternative of not moving at all. In fact, it has
been observed that obese persons tend
to stand significantly less often and for
shorter durations than lean persons.2 It
is a result that lines up with simple
mathematics—if a person is standing
up, using the energy of muscle contraction and relaxation in the legs to gain
elevation, and continuing muscle adjustments to remain standing, he or she
is by default using more energy than it
takes to stay sitting. It sounds rudimentary, but the most relevant advice a dietetics practitioner can offer a sedentary patient is simply to move. No
matter how minor it seems, as long as
patients are moving, they are not sitting—and that is what matters.
Sharing advice and information on
sedentarism is important in the modern health world, but a common theme
among research of the past decade has
been to look toward the future. Healthy
diet and a minimum amount of dedicated exercise continue to dominate
professional guidance, and less attention is currently paid to reducing sedentary behavior. But there is a call to
consider altering guidelines, in the
United States and around the world, to
incorporate the distinct concept of sedentarism into the preventative health
care lexicon. It is unlikely that the necessity of this new focus on sedentarism will decrease at any point in the
near future, as “modern humans may
still not have reached the historic pinnacle of physical inactivity.”22 And with the
1128
growing prevalence of sitting, both at
work and at home, it will become increasingly important to understand the
serious health risks of sedentarism. It is
unlikely that “SURGEON GENERAL’S
WARNING: Excessive Sitting May Increase Risk of Heart Disease, Diabetes,
High Blood Pressure, and Death” will
soon appear on chairs or couches, but
dietetics practitioners and health care
professionals should continue to guide
patients away from their seats and toward more active lives all the same.
in children and adolescents.
2012;307(7):704-712.
11.
Hagan P. Sitting for seven hours a day
“raises diabetes risk in women.” The Daily
Mail website. http://www.dailymail.co.uk/
health/article-2104850/Sitting-seven-hoursday-raises-diabetes-risk-women.html. Accessed February 29, 2012.
12.
Brownson RC, Boehmer TK. Patterns and
trends in physical activity, occupation, transportation, land use, and sedentary behavior.
http://onlinepubs.trb.org/onlinepubs/archive/
downloads/sr282papers/sr282Brownson.pdf.
Accessed February 1, 2012.
13.
Mulvihill K. Healthwatch: Sitting vs.
Smoking. CBS San Francisco website. http://
sanfrancisco.cbslocal.com/2011/06/08/
healthwatch-sitting-vs-smoking/. Accessed
February 23, 2012.
Tudor-Locke C, Leonardi C, Johnson WD,
Katzmarzyk PT. Time spent in physical activity and sedentary behaviors on the
working day: The American time use survey. J Occup Environ Med. 2011;53(12):
1382-1387.
14.
Hamilton MT, Healy GN, Dunstan DW, Zderic TW, Owen N. Too little exercise and
too much sitting: Inactivity physiology
and the need for new recommendations
on sedentary behavior. Current Cardiovascular Risk Reports. 2008;2(4):292-298.
Church TS, Thomas DM, Tudor-Locke C, et
al. Trends over 5 decades in US occuptional-related physical activity and their
associations with obesity. PLoS ONE. 2011;
6(5):1-6.
15.
Sisson SB, Camhi SM, Church TS, et al. Leisure time sedentary behavior, occupational/domestic physical activity, and metabolic syndrome in U.S men and women.
Metabolic Syndrome and Related Disorders.
2009;7(6):529-536.
Carlton J. Standing desks are on the rise. The
Wall Street Journal: San Francisco Bay
Area website. http://online.wsj.com/article/
SB10001424053111904199404576541011003270644.html. Accessed February 24,
2012.
16.
Juststand.org resource page. http://www.
juststand.org/. Accessed February 24,
2012.
17.
Hancox RJ, Milne BJ, Poulton R. Association
between childhood and adolescent television viewing and adult health: A longitudinal birth cohort study. Lancet. 2004;
364(9430):257-262.
18.
The Telegraph health news. Unhealthy lifestyle “ingrained by age 16.” http://
www.telegraph.co.uk/health/healthnews/
8233509/Unhealthy-lifestyle-ingrained-byage-16.html. Accessed December 15, 2011.
19.
Boone-Heinonen J, Rouz AVD, Kiefe CI, et
al. Neighborhood socioeconomic status
predictors of physical activity through
young to middle adulthood: The CARDIA
study. Soc Sci Med. 2011;72(5):641-649.
20.
Brownson RC, Baker EA, Housemann RA,
Brennan LK, Bacak SJ. Environmental and
policy determinants of physical activity in
the United States. Am J Pub Health. 2001;
91(12):1995-2003.
21.
Healy GN, Dunstan DW, Salmon J, et al.
Breaks in sedentary time: Beneficial associations with metabolic risks. Diabetes
Care. 2008;31(4):661-666.
22.
Hamilton MT, Hamilton DG, Zderic TW.
Role of low energy expenditure and sitting
in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Diabetes. 2007;56(11):2655-2667.
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