March 29, 2013
Vicious Cycle: Obesity’s Effect On Physical Activity
[ Watch the Video: Obesity Leads to Decreases in Physical Activity ]
April Flowers for redOrbit.com - Your Universe Online
For decades, researchers have studied physical activity and its relation to obesity. Almost no one, however, has studied the reverse — obesity's effect on physical activity.
A new study from Brigham Young University (BYU) looked at the other side of the equation to determine if obesity leads to less activity. Not surprisingly, the findings confirmed what everyone has assumed all along.
“Most people talk about it as if it´s a cycle,” BYU exercise science professor Larry Tucker said. “Half of the cycle has been studied almost without limit. This is the first study of its kind, in many ways, looking at obesity leading to decreases in physical activity over time.”
The research team attached an accelerometer, which measures actual movement and intensity of activity, to more than 250 participants to study this reciprocal effect. Prior research has relied upon less-dependable self-reported data.
“Roughly 35 percent of the population reports that they´re regularly active,” Tucker, an epidemiologist who has conducted many studies on obesity and its contributing factors, said. “When you actually put an accelerometer on adults and follow them for many days, only about 5 to 7 percent are actually regularly active. We used an objective measure so we could determine genuine movement, not just wishful thinking.”
The 254 participants — all of which were female and 124 of which were considered obese — were instructed to wear the accelerometer for seven consecutive days at the beginning of the study. They were asked to wear the device again 20 months later for another week.
The study, published online ahead of print in the journal Obesity, found that on average the obese subjects' physical activity dropped by 8 percent over the 20 months. This loss of activity is equivalent to decreasing moderate to vigorous physical activity by 28 minutes per week. Non-obese participants, in contrast, showed essentially no change in the amount of physical activity they were participating in weekly.
Tucker and his colleagues, graduate student Jared M. Tucker and exercise professors James LeCheminant and Bruce Bailey, were not shocked by these results. In fact, they had assumed the study would confirm this destructive cycle. However, they say that the results provide more understanding into how the cycle works and how it can be stopped. The study also offers more insight into the measurement methods researchers use, and how unreliable self-reporting can be.
“It´s not rocket science, and it´s very logical,” Tucker said. “It just hasn´t been studied using high quality measurement methods and with a large sample size. This provides scientists with more ammunition to understand how inactivity leads to weight gain and weight gain leads to less activity. This cycle, or spiral, is probably continuous over decades of life.”