Why do some people love working out, while others loathe it? If rats are any indication, the will to be active is at least partly genetic, according to a 2013 University of Missouri finding. And according to new research published online in the Journal of Physiology, those rats with a genetic predisposition toward being active are also more mentally mature than rats bred to be lazier.
Exercise geneticist Frank Booth, Ph.D., of the University of Missouri, is part of the research group that published both findings.
"What we're finding is that physical activity is linked to the maturing of neural networks in the brain," said Booth to The Huffington Post. There are at least two possible explanations for this: Either the genes that encourage physical activity also cause the brain to grow, or exercise itself helps to develop those neural pathways in young, pliable brains.
Booth's team took dozens of rats and identified the 26 best runners and the 26 worst runners. They bred the active rats with each other and the lazy rats (he called them "couch potato rats") with each other. After 10 generations of repeating this breeding process, the rats who were descended from the exercise-prone line chose to run 10 times more than the couch potato descendants.
Then, he examined the brains of the runner rats and lazy rats and found that the runner rats had more mature neuron cells in them, which means the neural pathways in their brains developed more quickly than the lazy rats.
Other recent genetic studies show that people may be genetically predisposed to procrastinate, be more anxious, be obese and even hate cilantro.
But, like those other genetic predispositions, laziness genes don't have to be destiny. For example, Booth notes that rats born from "couch potato" rat parents were actually able to stave off their genetic destiny when he gave them a running wheel very early in life.
"Most complex behaviors are never determined 100 percent by genetics or 100 percent by environment," said Booth. "How the brain is used may make pathways in the brain that might be more fixed for life." Additionally, exercise has also been shown to change one's DNA by altering the expression of genes.
Booth notes that more research is needed, but he is excited about the implications his research could have on encouraging more adults to have active lifestyles. Namely: Start 'em young.
"If we keep kids active instead of letting them sit in front of a computer, would that have an effect on adult health?" Booth mused.