Sedentary white women are more likely to become obese

Obesity is climbing steadily among American women and an inactive lifestyle is one risk factor. A new study finds that sedentary white women are more apt to become obese than are sedentary African-American women.

Researchers looked at data from 22,948 African-American women and 7,830 white women in 12 Southeastern U.S. states, where obesity is most prevalent. Participants, who mostly were in their fifth decade, were enrollees in the ongoing Southern Community Cohort Study between 2002 and 2006.

"The odds of severe obesity were nearly 4.5 times higher in white women and 1.5 times higher in black women in the highest quartile of sedentary behavior," according to researchers led by Maciej Buchowski, Ph.D., director of the energy balance laboratory at Vanderbilt University.

Buchowski said the reasons for the racial disparities remain unclear, because they did not do a controlled trial. He said he suspects that there could be some cultural explanation or difference in metabolism between the two groups, or perhaps African-America women are more active during sedentary time — cooking or doing other chores while watching TV.

The study appears online and in the August issue of the American Journal of Preventive Medicine.

"The key take-home message here is that reducing time in sedentary behavior is important," Buchowski said. "Our population was economically disadvantaged, so it is unlikely that they could join a club to participate in structured physical activity." Still, he said, "women do not need to walk for half an hour, but they can spend less time sitting. They can walk around the house, for example, or juggle a small bottle of water in their hands to increase their energy output without much effort.

"Remember — every calorie counts," he said. "These small changes could also be helpful in preventing obesity in the first place."

Amy Luke, Ph.D., associate professor of preventive medicine and epidemiology at Loyola University Chicago, who was not involved in this research, suggested that increased sedentary behavior might be a result, rather than a cause, of obesity.

"It must also be recognized that the data from this study are self-reported and finding associations between activity and obesity is not uncommon with questionnaires," Luke said. "Curiously, almost no studies utilizing objective measures of physical activity have found any relationship between physical activity and weight gain among women."

Buchowski MS, et al. Physical activity and obesity gap between black and white women in the Southeastern U.S. Am J Prev Med 39(2), 2010.