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Fit People Burn Fat Faster

Blood Molecules Reveal 'Metabolic Signatures' of Fitness, Heart Disease

Fitness in a Bottle? continued...

"When we exposed muscle cells to some of the metabolites that increase after exercise, we found they turned on an important gene that regulates the ability to use glucose [sugar] in fats," Lewis says. "So exercise through these small molecules that are released can stimulate expression of genes that are important to our metabolism."

Indeed, one gene activated by these exercise-associated molecules is nur77, a gene that helps control how the body burns or stores sugar and fat.

"If you look at a sports drink label, you'll see the drink contains handfuls of small molecules. But think of supplementing that drink with all these molecules we now know the body uses up during exercise," Lewis says. "So you can imagine we might be able to use these findings to craft the next generation of sports drinks."

And by studying the metabolic profiles of people with heart disease and other conditions, the researchers also hope to learn whether certain metabolites -- or drugs that mimic their action -- can be therapeutic.

But if all we want to do is lose weight, all the small molecules in the world might not be enough, cautions Andrew S. Greenberg, MD, director of the obesity and metabolism laboratory and the center on aging at Tufts University.

"Just because you have these metabolites does not mean that if you put them into your muscles you would be fit," Greenberg tells WebMD. "You don't just get on a treadmill and burn fat. It takes a long-term process of resetting the thermostat of how your body responds to exercise."

Exercise is just one part of the fitness equation, Greenberg says. Diet is the other.

But Joshua C. Munger, PhD, assistant professor of biochemistry and biophysics at Rochester University, notes that the Lewis study is breaking new ground in helping scientists understand the benefits of fitness.

"We understand that it is good for you to get plenty of exercise, but it is not clear exactly where the benefit lies," Munger tells WebMD. "The enticing question raised by the Lewis study is whether these metabolites could play a causal role in modulating the pathways leading to fitness."

The Lewis/Gerszten study appears in the May 26 online issue of Science Translational Medicine.

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