FRIDAY, April 5, 2013 (HealthDay News) -- Women who struggle with chronic obesity end up engaging in less and less routine physical activity, new research shows, confirming what may seem obvious to some.
The investigating team acknowledged that their observation so clearly aligns with conventional wisdom that it would be hard to describe it as "rocket science." But they say theirs is the first study to rigorously establish what most scientists have long presumed to be the case: that obesity does indeed have a negative impact on an individual's activity habits.
"An abundance of research has focused on factors that increase [the risk for] obesity, due to the many chronic diseases and conditions associated with it," said study lead author Jared Tucker, currently a senior epidemiologist at the Helen DeVos Children's Hospital in Grand Rapids, Mich. "And rightly so."
"However, physical inactivity is also independently associated with many of the same chronic diseases, including cardiovascular disease and type 2 diabetes," Tucker added. "But we don't often think about factors that influence activity levels."
Tucker was a graduate student when the research, reported online recently in the journal Obesity, was conducted.
"Our study suggests that obesity likely increases the risk of reducing physical activity levels in women," Tucker said. "Therefore, it appears that physical inactivity and obesity may be involved in a feedback loop, in which lower levels of activity lead to weight gain, which then leads to lower levels of activity."
To explore how obesity could depress activity levels among women, the authors focused on more than 250 middle-aged women living in the Mountain West region of the United States. Roughly half the participants were diagnosed as obese.
Rather than ask the women to self-report their activity routines -- a study method that can undermine reliability -- the team attached belt-strapped accelerometers to all the study participants. The small device measures movement of various accelerations and intensities. For a week, all the women were told to wear the straps throughout their day, except when exposed to water, such as while showering.
On average, the women wore the straps for nearly 14 hours out of the 15-hour daytime period (defined as 7 a.m. to 10 p.m.). This allowed the team to assess total time spent engaged in daily light, moderate or vigorous physical activity.
Body composition assessments were conducted just before the accelerometer monitoring began and again 20 months later. In turn, after the 20-month re-assessment, the women were again asked to wear the accelerometers for another week of activity monitoring.
The result: Among the obese participants, physical activity was found to drop by 8 percent overall over the course of the 20-month study period. This was equivalent to a loss of 28 active minutes per week, the researchers said.
Non-obese women, on the other hand, showed no drop in their physical activity routines.
"This finding," Tucker said, "highlights the importance of maintaining an active lifestyle and a healthy weight in order to prevent the start of this potential cycle of increasing risks."
Lona Sandon, a registered dietitian and assistant professor of clinical nutrition at the University of Texas Southwestern in Dallas, said the viciousness of this cycle means this is often easier said than done.
"What we do know is that obesity is clearly related to more sedentary behavior," Sandon said. "But is it that they move less and become obese, or because they're obese that they move less?"
Sandon said there are many reasons an obese woman would stop being active.
"Certainly, when you become obese it's just harder to move your body, and you become winded or easily fatigued with very little activity," she said. "S you would just plain avoid it for that reason."
Psychological issues also come into play, Sandon said.
"Being obese gets tied to emotion and body image. You don't want people watching you. You don't feel comfortable going to a gym or a fitness class because people may be staring," she said. "Low self-esteem, poor body image and depression also oftentimes go along with obesity. There's a lack of confidence that they can lose the weight, and that in trying to do it they'll just bring unwanted attention to themselves."
The cycle of obesity and inactivity "is a very complicated and difficult situation," Sandon said.
For more on physical activity recommendations, visit the U.S. National Heart, Lung, and Blood Institute.