SAN JOSE, Calif. – Some people stay fit and live to a ripe old age, despite never bothering to exercise. Why is that?
A report puts scientists one step closer to an answer.
Researchers from the United States and Norway ran rats on a treadmill until they were pooped.
They bred the best runners with each other, and did the same with those that tired most easily, until they had superjocks and superwimps with vastly different capacities for exercise – and prospects for future health.
The average rodent jock could run 42 minutes without stopping; the average wimp, just 14 minutes.
The least-fit rats gained more weight as they aged and scored worse on a number of measures that lead to heart disease and diabetes.
The results confirm that some rats – and, by extension, some people – are genetically more fit than others, and that this genetic legacy has an impact on health, said Steven L. Britton, a researcher at the University of Michigan and one of the authors of the report.
Probing further, the researchers found defects in the mitochondria of the wimpy rats – the power plants within each cell that determine how well it can function. While this does not prove a link to disease, it does lend weight to that idea, which has been raised in half a dozen previous studies, they wrote.
“There may be genetic markers right down in the muscle cells that determine an animal’s fitness – that determine how well it can process oxygen and produce energy,” said Jonathan Myers, an exercise physiologist at the Veterans Affairs Palo Alto Health Care System who was not involved in the study.
But while the results are provocative and important, he said, they don’t address the major reasons why the United States and other countries are facing an epidemic of obesity.
The incidence of obesity in the United States doubled in the 1990s, he said, with a parallel increase in what is known as metabolic syndrome – a cluster of problems that lead to heart disease and diabetes.
“Did our gene pool change? Of course it didn’t,” Myers said. “That takes centuries and centuries.” So while genetics might be a factor in fitness, lifestyle – from overeating to lack of exercise – “sort of blows that stuff away.”
The good news, he and other researchers said, is that almost everyone can improve fitness level and health by exercising.
The same was true of the wimpy rats. After six weeks of exercise, they improved on all but one of a dozen measures of health risk – although not as much as their athletic counterparts did.
Paul Williams, a health researcher at Lawrence Berkeley National Laboratory who has been studying similar issues in humans, said the new study offers insights into the role of genetics in fitness.
He said his studies suggest that men with high levels of so-called good cholesterol, or HDL, may be more likely to take up running, perhaps because it is easier for them.
“What this is showing, and what our earlier results suggest, is that it may not be just that people who are active are healthier, but that there is some other genetic component that is related both to their being healthier and to their being able to participate in vigorous exercise,” Williams said.
By teasing out the role of genetics in fitness, scientists hope to find markers that allow them to predict which people are at high risk of developing metabolic syndrome.
This could allow them to start preventive measures in childhood, and maybe even develop a treatment that works like exercise in a bottle. “We know that if there was a drug that did what exercise does, it would be quite a godsend,” Williams said.
However, those are still distant goals, said Myers, who studies the impact of fitness on health.
“If we could draw someone’s blood and say, “There are the genes for fitness,’ that would be great,” he said. “But that day may never come.”
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(c) 2005, San Jose Mercury News (San Jose, Calif.).
Visit Mercury Center, the World Wide Web site of the Mercury News, at http://www.bayarea.com/mld/mercurynews
Distributed by Knight Ridder/Tribune Information Services.
AP-NY-01-21-05 1203EST
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