ST. LOUIS - Couch-potato-itis may be genetic, rat studies at the University of Missouri-Columbia seem to indicate. The findings may eventually translate to sedentary humans.
Frank Booth, professor of biomedical sciences, said the experiments have shown that it's possible to be predisposed to being lazy, an important step for finding the causes of obesity in humans, including children.
Booth's research team has spent four years breeding rats that exhibited traits of either extreme activity or laziness. They gave dozens of rats running wheels and measured how much each rat willingly ran on its wheel over six days. They then bred the top 26 runners with one another and bred the bottom 26 runners with one another.
After 10 generations, tests showed different genetic differences between the active rats and the inactive rats, Booth said. Active rats spent exponentially more time on the running wheels than did the sedentary rats.
Once the researchers created their "super runner" and "couch potato" rats, they studied the levels of mitochondria -- parts of cells that burn energy -- in muscle cells, compared body composition and conducted genetic evaluations.
Also, they found 36 genes that seem to play a role in predisposition to physical activity motivation, or the lack of it.
The findings opened the door to more questions, Booth said, and the research that needs to follow is considerable.
--The active group had higher levels of anxiety; the inactive group tended to be more laid back. That brings questions of mental health into the mix, he said. For example, was the motivation to run due to attempting to relieve minor depression that the sedentary rats didn't have?
--The examinations showed the genetic influences were more likely from a combination of effects from groups of genes and not simply one active-lazy gene.
--Do the genetic differences increase the activity or increase the desire to be active?
--Can what actually triggers the rat conduct be altered?
Booth has studied the effects of inactivity for decades. He spent 24 years in Houston, where he worked under a grant from NASA for animal studies on the effects of inactivity that could translate to astronauts.
Since arriving at Mizzou more than 13 years ago, he has pondered what could be done about obesity among people and whether his work could help turn around America's worst epidemic. "We know of 35 conditions that can occur from inactivity," he said.
Studies show the majority of American adults get less than 30 minutes of exercise a day, which is the minimum recommended by federal guidelines, and that percentage increases as people get older, he said. Maybe getting older isn't the issue, he said.
Over the years, he has concluded that inactivity is acquired. "Just look at a 1-year-old child, so active his parents wish he'd be inactive for a while," Booth said.
But over the life span, activity levels decrease, he said, and the reasons why aren't so simple as people just become sedentary as they get older, even though that's what happens. Studies show "people who are motivated are the ones who increase their activity," he said.
Booth wrote in one of his documents about the study, "It would be very useful to know if a person is genetically predisposed to having a lack of motivation to exercise, because that could potentially make them more likely to grow obese," Booth said.
The study is in the April 3 edition of the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. ___