WASHINGTON - Gene may explain why some people are lazy, said a new study released by the University of Missouri on Monday.

"We have shown that it is possible to be genetically predisposed to being lazy," said study author Frank Booth, a professor from the Department of Physiology, School of Medicine. "This could be an important step in identifying additional causes for obesity in humans."

Booth and his fellow Michael Roberts were able to selectively breed rats that exhibited traits of either extreme activity or extreme laziness. These rats indicate that genetics could play a role in exercise motivation, even in humans, according to the study published in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology.

"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," said Booth.

Booth put rats in cages with running wheels and measured how much each rat willingly ran on their wheels during a six-day period. They then bred the top 26 runners with each other and bred the 26 rats that ran the least with each other. They repeated this process through 10 generations and found that the line of running rats chose to run 10 times more than the line of "lazy" rats.

Once the researchers created their "super runner" and "couch potato" rats, they studied the levels of mitochondria in muscle cells, compared body composition and conducted thorough genetic evaluations through RNA deep sequencing of each rat.

"While we found minor differences in the body composition and levels of mitochondria in muscle cells of the rats, the most important thing we identified were the genetic differences between the two lines of rats," Roberts said.

"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," he said.

The researchers said they plan on continuing their research to explore the effects each gene has on motivation to exercise.