Laziness may be genetic, according to a study by researchers from the University of Missouri.
By selectively breeding rats that exhibited traits of either extreme activity or laziness, researchers Frank Booth and post-doctoral fellow Michael Roberts found they were able to form two very different groups when it came to the desire to move around.
"We have shown that it is possible to be genetically predisposed to being lazy," Booth said in an article published on the school's site.
Knowing this, he said, may help identify additional causes for obesity in humans as well as shed light on the dramatic increase in childhood obesity currently taking place in the United States.
In order to measure the rats' attitude toward activity, Booth and Roberts put them in cages with running wheels for a six-day period and measured how much each rat used theirs.
The scientists then bred the top 26 runners with each other, and the top 26 non-runners with each other. This was repeated through 10 generations, upon which Booth and Roberts found that those bred from the first group ran 10 times more than those in the latter.
Analyzing them on a deeper level, the researchers said they found not only minor differences in body composition and levels of mitochondria in the muscle cells between the groups, but actual genetic differences.
"Out of more than 17,000 different genes in one part of the brain, we identified 36 genes that may play a role in predisposition to physical activity motivation," Booth said.
The study was published in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology on April 3, 2013.