Health & Family

Laziness your vice? Blame it on mice

If you hate to exercise, don't automatically blame it on laziness. It could be in your genes.

Researchers at UNC Charlotte say experiments with mice show some are more energetic than others, based on heredity.

“Can you be born a couch potato?” asked Tim Lightfoot, professor of kinesiology at UNCC. “In exercise physiology, we didn't used to think so, but now I would say most definitely you can.”

Lightfoot and his research colleagues recently completed two studies as part of a $1.7 million, five-year grant from the National Institutes of Health.

The first, published in the journal Physiological Genomics, reports that six chromosomal locations in mice are connected to the inheritance of a trait for high physical activity. The second, published in the Journal of Heredity, identifies 17 more sites.

Together, these genes account for about 84 percent of inherited behavioral differences between zippy mice and slothful ones, Lightfoot said.

He and his colleagues worked with strains of mice ranging from “high-active” to “aggressively sedentary” when faced with an exercise wheel.

“Many of these mice will run anywhere from five to eight miles a day,” Lightfoot said. “Scale that up to humans, and it's 40 to 45 miles a day.”

The lazy mice piled wood shavings on the wheel so it couldn't turn, Lightfoot said. They used it as a bed or a toilet, he said, just as some people use home treadmills as a place to hang their clothes.

UNCC researchers bred peppy mice with slacker mice and then observed the activity levels of their grandchildren.

What surprised Lightfoot was that three-fourths of the grandchildren inherited the high-active trait.

“I kind of dreaded that they were going to be low-active,” Lightfoot said. “But the chances of you being born the opposite of a couch potato is very good.”

(What's a good name for “opposite of couch potato”? Lightfoot is searching for the appropriate vegetable metaphor. He suggested “active asparagus” but agrees it doesn't have quite the right ring.)

This fall, Lightfoot's group plans to apply for a grant to expand its research to humans. He would like to collect “activity data” from human subjects and take DNA samples to determine if genes correspond to activity levels the way they do in mice.

This could be useful because people born with genes that predispose them to inactivity could be given specific exercise plans to get them active and keep them active, Lightfoot said.

Some day, he said, maybe we'll be able to alter our predispositions by turning certain genes on or off.

“Exercise is the cheapest medicine,” he said. “Anything we can do to get people active and to understand why people are not active will be helpful.”

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