Are you at work? Are you sitting down? You may want to get on
your feet, as a new study has found a link between occupational sitting
and increased risks of obesity, particularly among black women.
The researchers - from the School of Medicine and the Brown School at
Washington University in St. Louis, MO - publish their findings in Preventing Chronic Disease, a journal of the National Center for Chronic Disease Prevention and Health Promotion.
Health guidelines in the US suggest that adults undertake at least 150
minutes of moderate physical activity - such as brisk walking - or 75
minutes of vigorous intensity physical activity - such as jogging - each
week.
Individuals who have a sedentary lifestyle are at risk of several conditions, including high blood pressure, anxiety, depression and certain cancers. Additionally, overweight and obesity are recognized risk factors for several chronic diseases.
Unfortunately, prevalence of overweight and obesity in the US is on the
rise, with trends in obesity expected to increase medical costs by
$48-66 billion each year during the next 20 years.
Researchers from the latest study - led by Lin Yang, postdoctoral
research associate at the Prevention Research Center in St. Louis - say
until now, few studies have focused on the link between occupational
sitting and body mass index (BMI).
Given that many of us spend so much time at work, the team thought it
was important to investigate further. "The objective of this study was
to quantify the association between self-reported occupational sitting
time and BMI by gender and race," says Yang, "independent of time spent
in physical activity outside of work."
Link differed by gender and race
To conduct their study, between 2012-2013, the researchers interviewed
1,891 participants from four Missouri metropolitan areas, who were
between the ages of 21-65 years old and who were employed outside the
home for 20 or more hours per week. All participants were free of
physical limitations that prevented walking or bicycling.
The four metropolitan areas were St. Louis, Kansas City, Springfield and Columbia.
Participants answered questions on socio-demographic characteristics and
time spent sitting at work, and the researchers compared the link
between occupational sitting and BMI between men and women, as well as
between black and white women.
The team notes that the proportion of obese participants in their study
(33.6%) was similar to the proportion unveiled in a recent national
study (35.7%). Both men and women sat for an average of 3-6 hours at
work.
After adjusting for potential confounders, the researchers found
that, compared with women who spent 30 minutes or less of daily
sedentary time at their jobs, women who spent 31-180 minutes sitting
were 1.53 times more likely to be obese, and women who spent more than
360 minutes sitting were 1.70 times more likely.
However, the team notes that further stratification revealed this link
differed by race and held true for black women but not white women. And
this association was consistently observed across different amounts of
sitting time.
Additionally, the team did not observe any associations among men. Commenting on this finding, the researchers write:
"The lack of association between occupational sitting and weight status among men might be explained by the differences between men and women in physical activity preferences. Men are more active in leisure-time physical activity than women, and women tend to do less vigorous and more moderate activity compared with men."
Limitations to the study
Though the study had a fairly large sample size, there were several
limitations. Firstly, the researchers admit they were unable to conduct
race-stratified analyses for men, given that there was an insufficient
number of black men in their study.
Additionally, because of the cross-sectional design, the researchers
were unable to identify a causal relationship between occupational
sitting and weight. And the self-reported data means the results could
"be subject to response bias."
A further limitation lies in the location of the study sample; because
all participants lived in Missouri, the generalizability of the findings
to wider populations could be limited.
Still, Yang notes that only a few studies have so far examined the link
between occupational sitting and weight status, adding that, to the best
of their knowledge, "this is the first study to examine differences in
the association between occupational sitting and weight status among
African American women and white women."
The researchers conclude their study by writing:
"Sedentary time is accumulated in various settings, such as in the home and workplace and during transit. Given that adults can spend 8 or more hours per day at work, workplaces may be an ideal setting to reduce sedentary time through implementation of worksite policies or changes to the physical work environment."
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