Occupational sitting among women linked to obesity

Occupational sitting is associated with an increased likelihood of obesity, especially among black women, independent of occupational and leisure time physical activity, finds a new study from the School of Medicine and the Brown School at Washington University in St. Louis.

Few studies have examined the association between occupational sitting and body mass index (BMI), particularly among diverse populations.

The results of the study, "Occupational Sitting and Weight Status in a Diverse Sample of Employees in Midwest Metropolitan Cities, 2012-2013," were published Nov. 20 in the journal Preventing Chronic Disease.

"The objective of this study was to quantify the association between self-reported occupational sitting time and BMI by gender and race, independent of time spent in physical activity outside of work," said lead author Lin Yang, PhD, postdoctoral research associate at the Prevention Research Center, a collaboration between the School of Medicine, the Brown School and the Saint Louis University School of Public Health.

"To the best of our 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," Yang said.

The study was co-authored with Ross C. Brownson, PhD, the Bernard Becker Professor and director of the Prevention Research Center, and J. Aaron Hipp, PhD, assistant professor at the Brown School. Both are also faculty scholars at the Institute for Public Health.

In 2012 and 2013, participants residing in four Missouri metropolitan areas were interviewed via telephone. The interview included questions on socio-demographic characteristics and time spent sitting at work. The researchers examined the association between occupational sitting and BMI between men and women and between black and white women.

They found that average daily time spent by both men and women in occupational sitting was between three and six hours. Most participants in the study were overweight or obese.

"After adjusting for potential confounders, we found that African-American women in three categories of sitting time (31-180 minutes, 181-360 minutes, and more than 360 minutes) were approximately and consistently 2.5 times as likely to be obese as African-American women who reported sitting for 30 minutes or less, independent of occupational and leisure-time physical activity," the researchers wrote in the study.

This association was not seen among white women and no significant associations were found among men.

"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," the researchers wrote. "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."