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.”
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.”
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.”
Medical News Today recently reported on a study that suggested sedentary behavior in older adults may counteract the brain benefits of exercise.